2.1 The historical form of the optative prefix

As shown in Figure 1, I reconstruct the underlying form of the optative prefix in Pre-Dëne Sųłıné as */ʁʷɛ/, consisting of a voiced labio-uvular fricative, followed by a mid front vowel. This is very similar to the reconstructed PD (Proto Athapaskan) form as proposed by Krauss. Krauss (1969ː 63) reconstructs the PD optative prefix as *ɣʷə (with a labiovelar fricative), derived from an earlier *Gʷə (with a labio-uvular stop). Later in the same paper, he suggests that *Gʷə was itself derived from a combination of an imperfective prefix *Gα plus the irrealis prefix *ʊ, and that this combination had both a full grade *Gu and a reduced grade *Gʷə (1969: 69)—again very similar to my proposal in Figure 1. In reconstructing the Pre-Dëne Sųłıné optative prefix as *ʁʷɛ, I am following the methodological principle of reconstructing this intermediate stage as being as close as possible to the modern language, in the absence of evidence to the contrary. Thus, because the reflex of PD *ə is ɛ in Dëne Sųłıné (in prefixes), I reconstruct *ɛ rather than *ə; similarly, because the initial consonant of the opative prefix is spirantized in our earliest historical materials (e.g. LeGoff 1889, Li 1946), I reconstruct the initial consonant as *ʁʷ rather than *Gʷ. However, nothing in my analysis depends on these particular assumptions: formally, the analysis in §3.0 would be the same whether the Pre-Dëne Sųłıné optative were *Gʷə or *ʁʷɛ.

An alternative reconstruction of the optative was proposed by Leer (2000). Leer reconstructs the Proto Dene optative as *ʁυ, consisting of a voiced uvular fricative, followed by a reduced high-rounded vowel. In my opinion, there are three arguments against this proposal. The most direct evidence comes from the Tłı̨chǫ (Dogrib) language, in which, in the Behchokǫ̀ dialect as described by Ackroyd (1982), the reflex of the optative prefix is we [wɛ], as shown in Table 2. Ackroyd’s transcription system is given in regular type; my standardized re-transcription is added in brackets [ ]; in Tłı̨chǫ, Low tones are marked, while High tones are unmarked.

While we [wɛ] is a perfectly regular reflex of *Gʷə in prefix position (just as [ɛ] is a regular reflex of PD *ə in prefixes in Tłı̨chǫ more generally), a sound change from PD *υ > ɛ in Tłı̨chǫ prefix vowels has not been previously proposed.² A second argument against reconstructing the PD optative prefix as *ʁυ is that there are some Dene languages, including North Slavey and the Tetsǫ́t’ıné dialect of Dëne Sųłıné, where the optative prefix is indeed analyzed as /ɣu/ underlyingly. In these languages, there is no a ~ u alternation in the optative as in Table 1 and Figure 1. Rather, what we observe are either length alternations in the case of Tetsǫ́t’ıné (Jaker & Cardinal under review §5.8), or alternations between o and u in the case of North Slavey (Rice 1989: 548–550). It is probably not an accident that the optative prefix does not surface as wa³ or ha in languages where the underlying form is /ɣu/: the feature [low] will most likely not spread onto a vowel already specified as [round] (see §3.3). It follows that, at the time when the vowel alternation in Figure 1 arose historically, the vowel of the optative prefix was not *ʊ but rather *ɛ.

Finally, a sound change from PD *Gʷə to ɣu seems to be part of a more general sound change in this group of languages, involving the simplification of labialized dorsal consonants to plain velars, with rounding moving onto a neighbouring reduced vowel. Indeed, this is still a change in progress in some Dëne Sųłıné dialects, as shown in the examples in Table 3.

One final question regarding the optative in Pre-Dëne Sųłıné is: why not reconstruct the optative as */ʁʷʌ/, with the surface form the same as in the weak grade? This is what is assumed for the modern language by Li, who posits the basic form of the optative as ɣwa (1946ː 413), while Cook posits the basic form as either wa or ha, depending on the dialect (2004ː 39). Formally, it is certainly possible to derive ʁuː from ʁʷʌ via spreading of the feature [round] and de-linking of [low], and I will suggest that eventually the a ~ u alternation was indeed re-structured this way (§7.1). However, the goal of this paper is to explain the historical source of this alternation. If the PD optative was *Gʷə, as discussed previously, then at some point historically, either *ə or its reflex *ɛ must have lowered to *ʌ in the weak grade, and this lowering process is part of what needs to be explained.

2.2 The historical shapes of subject agreement prefixes

Next we will examine the reconstructed historical forms of the subject agreement prefixes. These are the prefixes which occur to the immediate right of the optative prefix (with the exception of the 3pl marker *qɛ, which occurs to the left), and it is the combination of the optative prefix with the subject agreement prefixes that results in either the full grade or the reduced grade of the optative, as in Figure 1. In Table 4, the subject agreement prefixes are highlighted in bold.

In the third person singular, subject agreement is zero (Ø), such that the optative prefix occurs by itself. The reconstruction of the 1^st person singular subject prefix in PD is problematic, in that it has been reconstructed with a special symbol <$>, whose precise phonetic quality is unclear (Krauss 1977: 36; Leer 2000: 105–106). By reconstructing this prefix as *ʃ for Pre-Dëne Sųłıné in Table 4, I am anticipating my conclusion in that the a ~ u alternations in the Dëne Sųłıné optative originated before the chain-shift which occurred in consonant place (which shifted *ʃ > s, *s > θ). Thus, *ʃ is the presumed historical source of modern s, prior to the chain shift (cf. Krauss 1982).

The reconstruction of the 1^st person dual/plural prefix in PD has also been controversial. Leer reconstructs this prefix as *iʼˑD-, a single syllable with a full constricted vowel (2000: 105). My reconstruction of this prefix as *íːd in Pre-Dëne Sųłıné would be the regular reflex of this form, following tonogenesis.⁵ On the other hand, Story reconstructs this prefix as originally trisyllabic, *əŋə^ʔdəD (1989: 500).⁶ For the purposes of this paper, distributional evidence suggests that the 1^st person dual/plural prefix behaves as a single, heavy syllable of the shape VːC, which is reflected in my proposed reconstruction.

The 2^nd person singular prefix in PD is reconstructed as *ŋʲə (Krauss & Leer 1981: 47; Leer 2000ː 105–106). Here again I follow the same logic as with the 1^st person singular prefix. In at least some modern Dëne Sųłıné dialects, there is evidence for an underlying palatal nasal /ɲ/, in the 2^nd person singular and perfective prefixes, which behaves differently from the alveolar nasal /n/ (Jaker & Cardinal under review: §1.2.2, 2.3). This is similar to what has been reported for Slave (Rice 1989: 61–62). The regular historical source of a modern palatal nasal /ɲ/, prior to the consonant shift, would be *ŋʲ (a palatalized velar nasal), which happens to be the same as the reconstructed PD consonant.

It has been observed that in some Dene languages, the 2^nd person singular prefix has two different forms. In modern Dëne Sųłıné, ne is the disjunct form, which occurs word-initially or after a so-called disjunct prefix, while ı̨ (with a nasal vowel) is the conjunct form, which occurs after one or more conjunct prefixes (see §2.3 for explanation of conjunct and disjunct), as was observed by Li (1946: 409, 411–412). Kari (1975) observed that distinct conjunct and disjunct forms of the 2^nd person singular also occur in Navajo and Tanaina. In both Navajo and Tanaina, Kari derives the conjunct form from the disjunct form by means of a rule of nasal absorption (1975: 335, 342). Similarly, for Pre-Dëne Sųłıné, I will treat *ŋʲɛ (the disjunct form) as the basic underlying form, from which the conjunct form *įː is derived via regular phonological rules (see §3.3).

In the 2^nd person plural, Krauss reconstructs the Proto Dene form of this prefix as *αχʷ, from a still earlier (Proto Dene-Eyak) *nαχʷ (1965ː 25). That is, with a reduced low vowel (*α). For Pre-Dëne Sųłıné, I assume that this prefix was already vowel-initial, as its combination with any preceding prefix behaves as a single syllable. I also assume that the labialization had already moved off of the final consonant and onto the preceding vowel, yielding *ʊχ, as shown in (5). This accounts for the rounded vowels found in the 2^nd person plural, both in the optative and elsewhere.

2.3 Left-to-right syllable counting and the Lexical Phonology model

At the beginning of this paper, I suggested that the a ~ u vowel alternation in Dëne Sųłıné can be thought of as representing different grades of the optative: the vowel a derives from the weak grade, while the vowel u derives from the strong grade. In this section, I will propose that the distribution of strong and weak grades can itself be derived from more general principles: stress and iambic feet. Specifically, I propose that Pre-Dëne Sųłıné was a quantity-sensitive, left-to-right iambic language; as part of this system, the strong grade of the optative was used in the strong position of an iambic foot, while the weak grade of the optative was used in the weak position of an iambic foot.

In a quantity-sensitive iambic system, the three canonical foot types are (Light-Heavy), (Light-Light), and (Heavy) (Hayes 1995: 65). A heavy syllable will always occupy the strong (stressed) position of a foot. If a heavy syllable follows a light syllable, they will form a (Light-Heavy) foot; if it follows another heavy syllable, it will form a (Heavy) foot by itself. If the iambic system is left-to-right, this means that, word-initially, a light syllable will always be in weak position, while a heavy syllable will always be in strong position.

In Table 5 we have a reconstruction of the paradigm for *hɛtɽaːɣ ‘cry’ (hɛtsaːɣ in the modern language). When the optative prefix is word-initial and is syllabified as part of a light syllable, it occurs in the weak grade, with the vowel *ʌ. We observe this in the 1^st person and 3^rd person singular forms (I assume that the 1sg subject prefix *ʃ did not contribute weight). Where the optative occurs as part of a heavy syllable, word-initially, it occurs in the strong grade, with the vowel *uː. We observe this in the 2^nd person singular, 1^st person plural and 2^nd person plural forms. In these cases, the word-initial heavy syllable is the result of coalescence rules at the segmental level, which must precede iambic foot parsing (see §3.4). Finally, the 3^rd person plural form is somewhat different. In this case, the first two syllables might be expected to form a (Light-Light) foot, but instead form a (Light-Heavy) foot, *(qɛ.ˈʁuː). I propose that this is an incidence of iambic lengthening. This process will be formalized in §3.4.

If the location of strong and weak positions of iambic feet depends on left-to-right syllable counting, one very important question is: from where exactly do we start counting? There is evidence that this is not necessarily the left edge of the prosodic word. Specifically, in all of our available sources, there are at least some prefixes which do not seem to “count,” as far as selecting the grade of the optative is concerned. To illustrate, let us compare two paradigms from Li (1946): the optative of hɛtsaɣ ‘cry’ as seen previously in Table 1, and the optative of tsʼɛˑðir ‘wake up’. In the latter case, we see that addition of the prefix tsʼɛ⁷ has no effect on the form of the optative, and the distribution of strong and weak grades of the optative is the same for both verbs. Forms are given in Li’s original transcription; paradigm cells using the strong grade are shaded grey.

Why does the prefix tsʼɛ seem to be ‘invisible’ in Table 6? According to the system originally developed by Li, prefixes can be divided into three groups: “conjunctive” (conjunct) prefixes which are closest to the stem, and “disjunctive” (disjunct) prefixes, which are farther from the stem (1946: 410), plus a third group of prefixes which are “between” conjunct and disjunct (1946: 410, 415). It is precisely these “in between” prefixes which exhibit variability in the published literature on Dëne Sųłıné optatives. Recall that, in the paradigms in Table 1, the 3^rd person plural form exhibits the strong grade of the optative in the example from Li (1946), huˑtsaɣ ‘they will cry’, whereas the same paradigm cell exhibits the weak grade in the examples from Cook (2004), hewajën and hehajën ‘they will sing’. This variability is related to the fact that hɛ is one of the prefixes which Li classifies as “in between” conjunct and disjunct. How might we model this variability?

From the perspective of Lexical Phonology (Kiparsky 1982, 1985), the categories of conjunct prefixes and disjunct prefixes correspond, loosely speaking, to stem level affixes and word level affixes, respectively. However, just as Li noted a third category of “in between” prefixes, Lexical Phonology approaches to Dene languages have realized the need for additional lexical levels, besides the Stem Level and Word Level, which are normally assumed for morphologically less complex languages. In fact, a total of 6 levels have been proposed (Hargus 1988, Jaker & Kiparsky under review), as illustrated in Figure 2.

Figure 2

Lexical Phonology model for Dëne Sųłıné (based on Jaker & Kiparsky, under review).

Under the Lexical Phonology model, the Dene verb is viewed as having the structure of a right-branching tree, with successive layers of prefixes being added outward from the stem. This particular structure has been termed the “Stem-Core” model (Halpern 1992; see also Randoja 1990). The prefixes which Li regarded as “in between” comprise the so-called “deictic” prefixes hɛ ‘3pl subject’, tsʼɛ ‘impersonal subject’, ʔɛ ‘unspecified object’, ʔɛdɛ ‘reflexive object’, and ɬɛ ‘reciprocal object’, as well as the object agreement prefixes including sɛ ‘1sg object’, nɛ ‘2sg object’, and yɛ ‘3sg object’ (Li 1946: 416; examples in Li’s orthography). These occupy positions 5–7 of the Dene verbal template,⁸ which correspond to Levels 3 and 4 of the Lexical Phonology model. Thus, from a Lexical Phonology perspective, these “in between” prefixes are added after the conjunct prefixes (at Level 2), but before the disjunct prefixes (at Level 5).

How does this relate to the optative? In Li’s data, we observe the strong grade of the optative following the Level 2 prefix nɛ (e.g. nustɛ́ ‘I will lie down’), following the Level 3 prefix hɛ (e.g. huˑtsaɣ ‘they will cry’) as well as the Level 4 prefix yɛ (e.g. yuˑɬtsi ‘he/she will make it) (1946: 413–414). On the other hand, in Cook’s data, we find the strong grade following a Level 2 prefix (e.g. nusdá ‘I will sit down (2004: 128)), but the weak grade following a Level 3 prefix (e.g. hehajën ‘they will sing’ (2004: 44)). From a Lexical Phonology perspective, it is actually part of the normal life-cycle of phonological processes that they become restricted to smaller and smaller morphological domains over time (Bermúdez-Otero 2015: 382–385). That is, phonological processes begin as ‘automatic’ phonetic implementation rules Postlexically, where they apply across word boundaries, and enter the lexical phonology at the point where they become restricted to individual words (Kiparsky 2015). In the present case, it appears that for Li’s speaker, François Mandeville, whom he recorded in 1928, and who was born in 1878 (Mandeville 2009), the syllable counting and stress assignment which resulted in selection of the strong or weak grade of the optative were Level 4 processes; by the time Cook collected his data in the later part of the 20^th century, the same alternation appears to have become a Level 2 process.⁹ Thus it would appear we have evidence, from the documentary linguistic record, of a phonological process becoming more restricted in its domain of application during the course of the 20^th century. While it is by no means necessary for such a change in the domain of application of a process to take place, it is consistent with what researchers in Lexical Phonology have observed of phonological processes generally. We will see in §7.0, however, that there continues to be variation between speakers in the behaviour of Level 3 prefixes, even to the present.

In reconstructing the source of the a ~ u alternation in Pre-Dëne Sųłıné, we may follow the above logic in reverse. That is, we may hypothesize that, as we go farther back in time, the domain of syllable counting and stress assignment affecting the optative involved larger and larger domains—including disjunct (Level 5) prefixes as well. However, in §4.0 we will see that, in the reconstructed scenario, assigning the optative alternation to Level 5 or Level 4 seems to predict the same result, which may have contributed to its re-analysis as a Level 4 process.

3.1 The Contrastivist Hypothesis

My solution to this apparent logical contradiction is to adopt underspecified representations (Archangeli 1988). Specifically, the particular version of underspecification theory I will adopt is contrastive specification, as formulated under the Contrastivist Hypothesis (CH) (Hall 2007; Dresher 2009). This hypothesis is stated in (1).

The phonological component of a language L operates only on those features which are necessary to distinguish the phonemes of L from one another.

Under this approach, the phonemes of a language are assigned their features through a procedure called the Successive Division Algorithm. This procedure is defined in (2).

The result of this procedure is that the phonemes of a language are represented in the form of a tree (see Figure 4), where each phoneme is specified for only those features which are necessary to distinguish it from other phonemes. In the case of Dëne Sųłıné, I propose that the vowels ʌ and aː are specified as [low], while the vowels ʊ and uː are specified as [round] (but not [high]). This means that it is possible for a single segment such as *ʁʷ to be specified as both [low] and [round], which can impart both an a-colouring and an u-colouring, respectively, to neighbouring vowels, without resulting in any logically contradictory feature specifications. The formal representation of feature spreading will be explained in §3.3, following discussion of the vowel inventory in §3.2. In the remainder of sections §3 and §4, I will simply assume that *ʁʷ is specified as [round] and [low]; in §5 and §6 I will justify and make fully explicit my assumptions regarding the place features of consonants.

3.2 Representation of the Dëne Sųłıné vowel inventory

The vowel inventory of modern Dëne Sųłıné has been controversial in the literature. The main question centers around the reflex of PD full and reduced vowels in Dëne Sųłıné: to what extent this contrast is maintained, and—in so far as it is—whether it should be thought of as a length contrast or a vowel quality contrast.

Cook, in his 1983 paper Chipewyan Vowels, described the Dëne Sųłıné language as exhibiting a six vowel system, as depicted in Figure 3.

Figure 3

Dëne Sųłıné (Chipewyan) vowel system according to Cook (1983: 416).

Figure 4

Feature hierarchy for Pre-Dëne Sųłıné surface vowels.¹⁰

Cook characterized this system as a vestige of the PD full ~ reduced vowel contrast, in the sense that he regarded ə as a reduced vowel, and all of the other vowels as full vowels (1983: 417). However, in his view, “full” and “reduced” refer to vowel quality only, representing peripheral versus central vowels, respectively. Thus, there is no underlying length contrast in Dëne Sųłıné, according to this view (Cook 1983: 424). Ackroyd (1976) reconstructed essentially the same vowel system for ‘Proto Northeast Athapaskan’ (PNEA), a hypothesized subgroup of languages comprising Tłı̨chǫ, Dëne Sųłıné, North Slavey, South Slavey, and possibly others. Thus, under this view, contrasts such as PD full *aː versus reduced *α, or full *uː versus reduced *ʊ, not only do not survive in modern Dëne Sųłıné, but had already undergone merger in the remote past.

In contrast to this view, Krauss (1983) reported work with a speaker from northern Saskatchewan, Mary Jane Kasyon, whose speech exhibited a vowel length contrast, even in monomorphemic stems. Krauss describes this contrast as being, in many cases, a direct reflex of the PD full ~ reduced vowel contrast. Thus Krauss finds modern Dëne Sųłıné [aˑ] from PD *aˑ, [ʌ] from PD *α, [eˑ] from PD *eˑ, [ɛ] from PD *ə, [o] and [ʊ] from PD *ʊ, and [uˑ] from PD *uˑ. Krauss suggests that the original PD full ~ reduced system may have evolved into a five vowel system with a long ~ short contrast, although there appears to be a gap in the inventory in that there is no short [i] (in stems).

Similarly, in later work, Cook described an underlying vowel length contrast in the dialect of Cold Lake, Alberta (Cook 2004: 28–30). For the Tetsǫ́t’ıné (Yellowknife) dialect, Haas (1968) noted long vowels (deriving from historical full vowels) in at least some stems, e.g. sɛtsʼáˑne ‘my wife’ (1968: 175). For this same dialect, a phonetic study by Jaker (2018) found evidence for an 8 vowel system: five full vowels [ɑː], [eː], [iː], [oː], [ʉː], and three reduced vowels, [ɐ], [ɘ], and [ɵ].

What we may draw from the above observations is that, if the PD contrast between full and reduced vowels, including the contrasts between *aː vs. *α and *uː vs. *ʊ, is preserved in at least some dialects of modern Dëne Sųłıné, then it is reasonable to infer that this set of contrasts was present at an earlier stage of the language as well. Therefore, for Pre-Dëne Sųłıné, I propose the vowel inventory shown in Figure 4. There are seven underlying vowels: four full vowels /aː/, /eː/, /iː/, /uː/, and three reduced vowels /ʌ/, /ə/, and /ʊ/. This is essentially the same as the reconstructed PD system. In addition, I propose two additional surface vowels, short [ɔ] and long [oː]. Short [ɔ] is the result of an allophonic vowel lowering process in stems which lowers /ʊ/ to [ɔ] before non-nasal codas, e.g. modern kʼɔθ ‘cloud’ from PD *qʼʊθ (Krauss 2005ː 91); long [oː] results from vowel coalescence in prefixes, i.e. /aː-ʊ/ → [oː]. Formally, I assume that any vowel which bears the feature [full] underlyingly will be interpreted by the phonology as bimoraic, while vowels which do not bear this feature will be interpreted as monomoraic (see Tuttle 1998: 196 for a similar claim regarding full and reduced vowels).

In terms of the Successive Division Algorithm (SDA) in (2), the proposed ordering of features in Pre-Dëne Sųłıné is [full] > [round] > [low] > [high]. There are two characteristics of the vowel hierarchy in Figure 4 which may be somewhat surprising. The first is that there is an asymmetry in the representation of vowel height, if we compare the rounded vowels to the unrounded vowels. Among the unrounded vowels, the contrast between phonetically high and mid vowels is represented by presence or absence of [high]. Thus, /iː/ is [high], while /eː/ lacks [high]. On the other hand, among the rounded vowels, the parallel contrast between phonetically high and mid vowels is represented by the presence or absence of [low]. Thus, [oː] and [ɔ] are [round][low], while /uː/ and /ʊ/ are merely [round] (and not [low]). There are three arguments to support this asymmetrical representation of vowel height. The first is evidence from morphophonemics, from the modern language. In modern Dëne Sųłıné, in verbal prefixes, /a/ and /u/ coalesce to form [o], as in /na-uh-l-zé/ → nóɬzé ‘you (pl) hunt (imperfective)’ (Cook 2004: 47; example given in Cook’s orthography); on the other hand, a similar coalescence of /a/ and /i/ to yield [e] is not attested. This asymmetry in coalescence patterns is predicted by the representations in Figure 4: whereas /ʌ/ or /aː/ can spread a [low] feature onto /ʊ/ or /uː/ to yield a vowel which is [low][round], spreading of a [low] feature onto /iː/ would yield a vowel which is [low][high]—a combination which is formally impossible. A second argument in favour of the asymmetric representation of vowel height is that there is evidence, historically, for a parallel asymmetry in the consonant system—this will be discussed in §6.0. Finally, the most important argument in favour of Figure 4 is that it allows for an elegant account of consonant-vowel interactions: each of the three vowel colourings which consonants may impart to neighbouring vowels in Dëne Sųłıné—the a-colouring, i-colouring, and u-colouring—can be accounted for by the spreading of just one feature from a vowel to a neighbouring consonant. Thus, the a-colouring results from spreading of [low], the u-colouring results from spreading of [round], and the i-colouring results from spreading of [high]. These interactions will be examined in more detail in §3.3.

The other characteristic of the representations in Figure 4 is that the phonological features used do not necessarily correspond to surface phonetic properties of the vowels. In particular, use of the feature [low] does not entail that the vowel is phonetically low: the vowels /ɔ/ and /oː/ bear the feature [low], but are phonetically mid vowels. In this case, one could think of the feature [low] as meaning “lower”: vowels which bear this feature are lower than they would otherwise be by default. Since, under this system [round] vowels are high by default, adding the feature [low] results in a vowel which is lower than a high vowel—i.e. a mid vowel. See Ghini (2001: 192) for a similar use of [low] to distinguish /o/ from /u/, in Miogliola.

3.3 Vowel alternations as feature spreading

In this section, I will provide a formal representational account of consonant-vowel interactions in Pre-Dëne Sųłıné, in terms of feature spreading. The basic facts to be accounted for are the three vowel colourings mentioned above. All three vowel colourings are relevant to a complete account of the optative: the i-colouring is associated with the 2^nd person singular subject prefix *ŋʲə, and helps explain why the 2^nd person singular paradigm cell (in the optative) exhibits the strong grade. The a-colouring and u-colouring are both associated with the optative prefix itself: the a-colouring is observed in the weak grade, while the u-colouring is observed in the strong grade.

The first step is to establish the feature-geometric representation of the vowels. I assume that, under a given class node, features are arranged in a one-dimensional, linear string, which reflects the ordering of features in the SDA, for that language (see Spahr 2014: 559 and Spahr 2016: 64–69 for a similar proposal). Regarding place features, following Padgett & NíChiosáin (1993), I employ two place nodes: the CPlace node, which hosts consonantal place features, and the VPlace node, which hosts vocalic place features. Thus, I assume that for PreDëne Sųłıné, vocalic features are arranged under the VPlace node as shown in Table 7.

Table 7

Vowel features under the VPlace node (Pre-Dëne Sųłıné).

Reduced Vowels	Full Vowels

We will begin by considering the i-colouring—that is, spreading of the feature [high], which occurs when either the 2^nd person singular subject prefix *ŋʲə is preceded by another conjunct prefix. This results in the so-called ‘conjunct form’ of these prefixes, which contains the full nasal vowel *įː. This alternation, between *ŋʲə ~ įː, has been reconstructed all the way back to PD (Krauss & Leer 1981). Even in modern Dëne Sųłıné, Li sometimes writes these forms with a long vowel, e.g. hįˑlaɬ ‘go to sleep!’ (Li 1946: 400).

If we assume that the conjunct form *[įː] is derived from the disjunct form */ŋʲɛ/ within the synchronic phonology of Pre-Dëne Sųłıné, this actually involves several phonological rules operating in concert: (a) raising of the preceding vowel from ə to iː, (b) syncope of the following vowel, (c) nasalization of the preceding vowel, and (d) deletion of the nasal consonant itself. Given the complexity of this process, the main question is: are any of these rules responsible for conditioning the others?

I propose that spreading of the feature [high], from *ŋʲ onto the preceding vowel, was the trigger for this entire set of rules. In particular, since in my reconstruction of the Pre-Dëne Sųłıné vowel system in Figure 4 and Table 7 there is a gap in the vowel inventory, such that there is no short [i] (similar to what Krauss (1983) observed for the modern language), spreading of the feature [high] onto a preceding vowel necessarily requires that the feature [full] also be inserted—otherwise, spreading of [high] would violate Structure Preservation (Kiparsky 1985). This is illustrated in Figure 5.

Figure 5

Representation of *əŋʲ → *iːŋʲ (spreading of [high], insertion of [full]).

This long vowel then triggers syncope of the vowel of the following syllable, i.e. iːŋʲɛ → iːŋʲ, which then triggers nasalization of iː to įː and deletion of the nasal consonant. This entire complex process will be formalized as a rule-based derivation in §3.4.

Next, we will examine the u-colouring—that is, spreading of the feature [round], which occurs in the strong grade of the optative. This process also involves insertion of the feature [full], though for a somewhat different set of reasons in different paradigm cells. In the 2^nd person singular form, the vowel following ʁʷ would already be full, since the set of rules which derive įː from ŋʲɛ (as discussed previously) would have already applied. Similarly, in the 1^st person plural form the vowel is also already full, while in the 2^nd person plural, the two adjacent reduced vowels would coalesce to form a full vowel, i.e. */ʁʷɛ-ʊh/ → ʁʷuːh → ʁuːh. Finally, in the 3^rd person plural form, I propose that the feature [full] is inserted as part of a proces of iambic lengthening, as shown in Figure 6 below.

Figure 6

Representation of *ʁʷə → *ʁuː (spreading of [round]).

Finally, we will examine the a-colouring which some consonants may impart onto neighbouring vowels, also called gamma lowering (Hargus 1988: 144). I assume that spreading of the feature [low], from *ʁʷ onto a neighbouring vowel, operates as a kind of default or “elsewhere” rule. This is illustrated in Figure 7.

Figure 7

Representation of *ʁʷə → *ʁʷʌ (spreading of [low]).

To summarize, we have seen that the representational system which I have proposed in this section, based on the Contrastive Hierarchy, is able to succinctly describe the three colourings which consonants may impart to neighbouring vowels as consisting of the spreading of just one feature: the a-colouring involves the spreading of [low], the i-colouring involves the spreading of [high], and the u-colouring involves the spreading of [round]. In some cases, the feature [full] is inserted as well. In the next section, we will examine how these feature spreading processes are conditioned by, and interact with, the prosodic environments described earlier in §2.3.

3.4 Prosodic conditioning

In §2.3 I provided an account of vowel alternations in the optative from a prosodic perspective, while in §3.3 I provided an account of the same alternation from a segmental perspective. In this section, I will integrate these two perspectives, by showing how feature spreading rules can be conditioned by their prosodic environment. My goal in this section will be to provide a complete derivation of the optative paradigm of the verb *hɛtɽaːɣ ‘cry’, as shown in Table 5.

First we will derive the singular forms: *ʁʷʌʃtɽaːɣ ‘I will cry’, *ʁųːtɽaːɣ ‘you (sg) will cry’, and *ʁʷʌtɽaːɣ ‘he/she will cry’. The first step is a formalization of the rules. The rule of [low] spreading, which occurs in the 1^st and 3^rd person singular forms, can be stated as in (3). In order for this rule to apply only in the “elsewhere” case, I have imposed a condition such that (3) applies only if spreading of [round] (to be defined in (9)) has not applied.

(3)	Spreading of [low]
	“The feature [low] spreads from a consonant onto the following vowel.”

CONDITION: Applies only if Spreading and de-linking of [round] (9) has not applied.

The set of rules involved in deriving the 2^nd person singular form is more complicated. Broadly speaking, this can be thought of as a two-step process: first the optative prefix *ʁʷɛ combines with the 2^nd person singular subject prefix ŋʲɛ to derive the conjunct form, */ʁʷɛ-ŋʲɛ/ → ʁʷįː, and subsequently the labialization from *ʁʷ moves onto the following vowel *ʁʷįː → *ʁųː The first rule in the series, which provides the ‘trigger’ for all of the following rules, is the spreading of [high] from *ŋʲ to the preceding vowel, as shown in (4).

(4)	Spreading of [high]

As discussed in §3.3, since short *[i] is, under the current proposal, not part of the vowel inventory for Pre-Dëne Sųłıné, the feature [full] must be inserted as well, in order to satisfy Structure Preservation. The rule for [full] insertion is shown in (5).

(5)	Insertion of [full]

The rules so far would yield *ʁʷiːŋʲɛ. In order to derive *ʁʷįː, we need a set of rules which will account for syncope of *ɛ, nasalization of the vowel *iː, and deletion of the nasal consonant in syllable coda position. These rules are given in (6)–(8).

(6)	Syncope of a reduced vowel following a full vowel
	“A monomoraic vowel deletes, when a bimoraic vowel occurs in the preceding syllable.”

In (6), I assume that any vowel which is [full] projects two moras on the moraic tier, while any vowel which lacks the feature [full] projects only one mora. The rule in (6) is formally stated in terms of moras rather than in terms of the feature [full] since, when using monovalent features, it is not possible to specify the target of a rule as lacking a certain feature (the rule would simply apply to all vowels).

(7)	Vowel nasalization

(8)	Nasal coda deletion

The rules presented so far would derive *ʁʷįː from */ʁʷɛ-ŋʲɛ/. There is one last step necessary in order to derive the desired output *ʁųː, and that is spreading and de-linking of the feature [round]. This rule applies only in the strong position of an iambic foot, as shown in (9).

(9)	Spreading and de-linking of [round]
	“The feature [round] de-links from a consonant and spreads onto a following vowel in the strong position of an iambic foot.”

This raises the question: what would motivate spreading and de-linking of the feature [round], in the strong position of an iambic foot? According to González (2003), there is a relationship between sonority and prosodic position. Specifically, syllables in prosodically weak positions prefer to have low-sonority nuclei and high-sonority onsets (e.g. wə), whereas syllables in prosodically strong positions prefer to have high-sonority nuclei and low-sonority onsets (e.g. ta). Regarding the vowels, if we interpret sonority in the strictest sense, referring only to aperture features, then the fact that [uː] occurs in the strong grade, while [ʌ] occurs in the weak grade, seems to run contrary to this proposed generalization—since [uː] is technically less sonorous than [ʌ].

I suggest instead that the locus of explanation for this vowel alternation is actually on the preceding consonant. Specifically, I suggest that spreading and de-linking of the feature [round] in the strong grade serves to make the onset consonant less sonorous, by removing its labial glide articulation. On the other hand, spreading of the feature [low] in the weak grade does not seem amenable to this type of explanation: in the mapping */ʁʷɛ/ → *ʁʷʌ, sonority of the onset consonant is unchanged, while the sonority of the vowel has increased—the opposite of what would be expected in prosodically weak position. Thus, while it is formally possible to formulate the rule of [low] spreading in (3) as applying only in the weak position of an iambic foot, this would imply a certain teleology which is probably not appropriate for this process. Rather, it seems better to think of the two rules, in (3) and (9), as disjunctive: [round] spreading (9) applies in the strong position of an iambic foot, while [low] spreading (3) applies elsewhere.

A derivation of the optative singular forms of the verb *hɛtɽaːɣ ‘cry’ is given in Table 8. Numbers in parentheses after each rule refer to the figure where that rule was defined.

The derivation in Table 8 could be summarized as follows: the segmental rules (4)–(8) feed Iambic Foot Construction, and the iambic feet which are constructed feed either spreading and de-linking of [round] (9) or spreading of [low] (3), disjunctively. Thus, in column (b), the rules (4)–(8) transform what would otherwise be a (Light-Light)(Heavy) prosodic pattern into a (Heavy)(Heavy) pattern. Since the optative prefix therefore falls in the strong position of an iambic foot, [round] spreading and de-linking apply. On the other hand, in columns (a) and (c), rules (4)–(8) do not apply, leaving the input (Light-Heavy) pattern unchanged. This places the optative prefix in the weak position of an iambic foot, and therefore [low] spreading applies instead.

We will now derive the plural forms *ʁúːtɽaːɣ ‘we will cry’, *ʁuːχtɽaːɣ ‘you (pl) will cry’, and *qɛʁuːtɽaːɣ ‘they will cry’, as seen previously in Table 5. Regarding the 1^st person plural form, in the mapping */ʁʷɛ-íːd-tɽaːɣ/ → *ʁʷíː.tɽaːɣ → *ʁúːtɽaːɣ, there is a technical issue which arises when the feature [round] spreads onto the vowel [iː], which is already specified as [high]: under the proposed vowel inventory in (12), there is no [high][round] vowel, and so the creation of such a vowel would violate Structure Preservation. Therefore, it is necessary that when [round] spreads onto the vowel [iː], the feature [high] be de-linked simultaneously, as shown in (10). Also, in the 1^st person plural, the coda consonant d of the 1^st person plural prefix *íːd must also be deleted in coda position, as shown in (11).

(10)	De-linking of [high] conditioned by [round] spreading

(11)	Coda d deletion

In the 2^nd person plural form, the main question is the formal representation of vowel coalescence, whereby */ʁʷɛ-ʊχ/ → ʁuːχ. That is, even prior to spreading and de-linking of [round] from the onset consonant *ʁʷ, the vowels ɛ and ʊ coalesce to form the full vowel uː, which I will assume consists of a single vocalic root node. For present purposes, I will collapse the entire coalescence process down to just two rules. I assume that each of the two input vowels, V₁ and V₂, is already associated with a mora underlyingly. The Coalescence rule in (12) de-links the mora from V₁ and associates it to V₂, and also de-links all place features of V₁ and re-associates them to V₂. V₁ is then deleted by stray erasure.

(12)	Coalescence

When the features of V₁ associate to V₂, any featural incompatibilities which arise will be resolved according to the language’s vowel strength hierarchy. The Contrastive Hierarchy predicts that the vowel (or consonant) strength hierarchy of a language will mirror the ordering of features and the SDA (Dresher 2009: 148). In (10), for example, we saw that the feature [round] displaces the feature [high], and indeed [round] is ordered before [high] in the feature hierarchy in Figure 4. Later, in §7.1, we will also see evidence that, in the modern language, [round] is stronger than [low], which is also predicted by Figure 4.

The result of the coalescence rule in (12) is an output vowel (V₂) which retains the strongest feature(s) of both vowels, and which has two moras. In order to be well-formed, however, a bimoraic vowel requires insertion of the feature [full], as in (13).

(13)	Insertion of [full]

Finally, we come to the 3^rd person plural form *qɛʁuːtɽaːɣ. In order to derive the long vowel uː in this form, we need to add a rule of iambic lengthening. I propose that this rule operates at the moraic level, changing a (Light-Light) iambic foot into a (Light-Heavy) foot (Prince 1990, 1991), which in turn results in insertion of the feature [full], as in (13). The rule of iambic lengthening is defined in (14).

(14)	Iambic Lengthening
	“A monomoraic vowel becomes bimoraic in the strong position of an iambic foot.”

A derivation of the plural forms is given in Table 9. Those rules which are active in this derivation are highlighted in bold.

In Table 9, the rule of [full] insertion must apply twice: after Coalescence (12) in columns (a) and (b), and after iambic lengthening in column (c). It is probably best to regard this rule as a persistent rule, which applies at any point in the derivation to repair mis-matches between mora count and the feature [full].

7.1 Vowel alternations as spreading of [round]

First I will present data from a conservative speaker, Allan Adam, now residing in Paddockwood, Saskatchewan (originally from Fond du Lac, Saskatchewan). Mr. Adam is also a trained professional Dëne Sųłıné interpreter and translator. Mr. Adam preserves labiovelar consonants in his speech, and also exhibits a contrast between full and reduced vowels. Thus, the phonological system for this speaker is very similar to the Dëne Sųłıné system described by Li (1933, 1946) many decades ago. The optative paradigm of hɛdʒən ‘sing’ is given in Table 17.

In Mr. Adam’s speech, the vowel length difference between [ʌ] and [uː] is very clear, such that the speaker even volunteered (without being asked directly), “it’s a long u sound. The u is long,” in reference to the 3^rd person plural form. This speaker also exhibits an interesting alternation between [ɣ] in the strong forms, and [w] in the weak forms—consistent with González’s (2003) predictions about the relationship between sonority and prosodic position.¹² Given that there is a surface alternation between [ɣ] and [w], and given that the speaker pronounces labiovelars elsewhere, it is reasonable to suppose that the optative prefix is still underlyingly /ɣʷʌ/ for this speaker. That being the case, the alternations in Mr. Adam’s optative paradigm can be analyzed in a very similar way to the reconstructed Pre-Dëne Sųłıné system examined in §3: the feature [round] spreads and de-links in the strong forms, in order to decease onset sonority. The only differences are that the vowel [ʌ] in the weak forms is not the result of a spreading process, but is underlying, and also /ɣʷ/ lenites to [w] in the weak forms (in this case, to increase onset sonority). Under this hypothesis, it is interesting to note that the feature [round] displaces—i.e. is stronger than—the feature [low], which it also outranks in the feature hierarchy in Figure 4. This is predicted by the CH.

7.2 Vowel alternations as phonologically conditioned allomorph selection

Next we will examine data from another speaker, Mr. Daniel Alphonse of Black Lake, Saskatchewan. Mr. Alphonse’s phonological system is also conservative in that it maintains a contrast between full and reduced vowels, as shown in Table 18.

The main difference between Mr. Alphonse’s dialect in Table 18, and Mr. Adam’s dialect in Table 17, is that Mr. Alphonse uses the consonant [w] for the optative prefix throughout the paradigm, rather than having a ɣ ~ w alternation. Given this fact, it is somewhat unlikely that one could posit /ɣʷʌ/ as the underlying form of the optative prefix for this speaker. Rather, under standard assumptions regarding phonological abstractness, the initial consonant must be re-structured to /w/ underlyingly.

This has two major consequences. The first is that it is no longer possible to analyze the vowel alternations in (41) as [round] spreading and de-linking in prosodically strong position. Recall from §3.4 that the whole point of [round] spreading is to reduce the sonority of the onset consonant where the rule applies; in this case, since the onset consonant is [w] regardless, such spreading is unmotivated. Therefore, the most likely alternative is that the strong and weak grades of the optative in Table 18 are chosen through phonologically conditioned allomorph selection. Phonologically conditioned allomorph selection is when a given morpheme has two (or more) underlying forms, and the phonology selects whichever allomorph would be most harmonic in a given environment (Kager 1996; Rubach & Booij 2001; Anderson 2008). Allomorph selection is used extensively by Hargus in her analysis of the Dene language Witsuwit’en (Hargus 2007: 671–730). In the case of Table 18, if the two allomorphs of the optative are /wʌ/ and /wuː/, what conditions the choice between them?

I suggest that, broadly speaking, the allomorphy is conditioned by stress. /wʌ/ is the default or “elsewhere” allomorph, because, being a light syllable, it can fit into the weak position of an iambic foot. However, /wuː/ is chosen where the syllable needs to be stressed or heavy for independent reasons. For example, the 2sg, 1pl, and 2pl forms all have an additional vowel as part of the subject agreement prefixes ne, íd, and uh, which add an extra mora and therefore constrain the output vowel to be long.

The only form which seems not to fit this line of explanation is the 3^rd person plural form, hɛwʌdʒən, where, on the surface, there appears to be a mis-match between stress and the choice of allomorph. However, this is actually the second major consequence of restructuring of the optative from /ɣʷʌ/ to /wʌ/ ~ /wuː/. Since the optative is a Level 2 (conjunct) prefix, at the point where it enters the derivation and the allomorphs are selected, it can only see other Level 2 (conjunct) prefixes. The prefix hɛ ‘3^rd person plural’ is only added later (at Level 3). Therefore, once the vowel alternations in the optative are re-analyzed as allomorph selection, it necessary follows that the choice of allomorph will only be sensitive to Level 2 prefixes.

7.3 Vowel alternations as morphologically conditioned allomorph selection

The third and final logical possibility listed in the dialect typology in Table 16 is a dialect which has lost both the labio-velar series as well as the full ~ reduced vowel contrast underlyingly. Cook, in his chapter on linguistic change and variation in Dëne Sųłıné, suggests that all dialects except Tadoule Lake, Manitoba have lost the labio-velar series (2004: 23), and all dialects except Cold Lake, Alberta have lost the full ~ reduced vowel contrast (2004: 28–30). Therefore, according to Cook, the majority of dialects would fall into this category (although more data are needed in order to verify this claim).

In such dialects, which have lost contrastive vowel length in prefixes, there would no longer be any way to phonologically derive the distribution of a and u vowels which we have seen. Rather, while we would still posit two allomorphs, /wa/ and /wu/ (note: these no longer differ in length), their distribution would be morphologically governed, based on morphosyntactic features. The most likely analysis would be that /wu/ is constrained to appear only when the subject is 2^nd person, or 1^st person plural, whereas /wa/ is the elsewhere allomorph.