Contributions to the concepts of reproductive cycles and the systematics of the scalaris group of the lizard genus Sceloporus

Abstract

The concept of parity type is proposed as a criterion of relation- ship among members of the Sceloporus aeneus-scalaris complex, with members of S. aeneus being regarded as and those of S. scalaris, as oviparous. The S. goidmani is regarded as a relative of S. aeneus , and S. a. subniger is not regarded as intermediate between S. scalaris and S. aeneus. The proposal by Davis and Smith that S. a. aeneus is oviparous and specifically distinct (as S. aeneus) from S. a. bicanthalis (as S. bicanthalis) is rejected. S. aeneus is hypothesized to have a biennial reproductive cycle. S. scalaris slevini auctorum is segregated into two subspecies: S. s. samcolemani subsp. nov. in the Sierra Oriental (northern end), and S. s. slevini sensu stricto in the Sierra Occidental (also northern end) of Mexico and of the adjacent United States. The systematics and phylogenetic history of the scalaris group of Sceloporus has long been viewed as enigmatic, beginning with the statement of the quandary by Smith (1939: 347-348) in explanation of the allocation of the northwestern member, slevini , to the species scalaris despite some contrary evidence. However, Smith and Pog- layen (1958: 13-15) allocated slevini to the species aeneus after another population exhibiting certain features of intermediacy be- tween the two polytypic species scalaris and aeneus was described (S. a. subniger) . Neither of the preceding accounts placed any overt emphasis upon parity types. Smith (1939: 332) made a passing comment that both oviparous and 4 'ovo viviparous species occur in the group. Evi- dence now available makes it certain that members of the scalaris complex are oviparous, and we here postulate that members of the aeneus complex are (a broader term, more certainly ap- plicable than ovoviviparity, which has come to imply absence of placental structures, whereas euviviparity implies their presence; both conditions exist in reptiles and only by microscopic techniques can they be determined). Anderson (1962) has demon- strated that slevini is oviparous, and accordingly its allocation with the scalaris complex is correct. The most critical doubt cast upon this hypothesis is the proposi- tion by Davis and Smith (1953: 102) that S. a. aeneus is oviparous, whereas S. a. bicanthalis is incontrovertibly (Smith, 1939: 356, and personal data). On this basis these taxa were elevated to specific status ( S. aeneus , S. bicanthalis) . The data provided in Davis and Smith, however, strongly suggest that in S. a. aeneus viviparity does occur, but on a two-year cycle. Ten of 28 females collected from 25 July to 15 August contained from 3 to 5 (average 4) large ova,