THE EVOLUTIONARY HISTORY OF PARTHENOGENETICCNEMIDOPHORUS LEMNISCATUS(SAURIA: TEIIDAE). II. MATERNAL ORIGIN AND AGE INFERRED FROM MITOCHONDRIAL DNA ANALYSES

Abstract

Restriction endonuclease analyses were performed on mitochondrial DNAs (mtDNAs) representing unisexual parthenogenetic (cytotypes A, B, and C) and bisexual (cytotypes D and E) populations of Amazonian lizards presently regarded as Cnemidophorus lemniscatus. The results of mtDNA cleavage map comparisons among these C. lemniscatus indicated that (1) there was no cleavage site variation among the unisexuals, (2) mtDNAs from the bisexual cytotypes D and E differed in sequence from one another by about 13%, and (3) mtDNAs from cytotypes A-C differed from those of cytotype D by about 5% and from those of cytotype E by about 13%. Higher resolution restriction fragment size comparisons confirmed the high degree of similarity among the unisexual mtDNAs, but identified 12 cleavage site variants among the 13 cytotype D mtDNAs examined. Both cladistic and phenetic (UPGMA) analyses of the data indicate that the unisexual and cytotype D mtDNAs form a single clade, suggesting that a female of cytotype D was the maternal progenitor of the unisexuals. The similarity among the unisexual mtDNAs and the variability among those of cytotype D suggest that the three unisexual cytotypes arose recently from a common maternal lineage. The mtDNA variability observed among cytotype D individuals has a strong geographic component, suggesting that the unisexuals arose from one or a few geographically proximal populations. The mtDNA comparisons also support the conclusion, based on allozyme comparisons (Sites et al., 1990, this issue), that cytotypes D and E, although presently allocated to C. lemniscatus, are separate species.

Mitochondrial DNA Analyses and the Origin and Relative Age of Parthenogenetic Cnemidophorus: Phylogenetic Constraints on Hybrid Origins

“…Bisexual species involved in the hybrid origins of parthenogenetic lineages of Cnemidophorus. Estimates of sequence divergence between mtDNAs (see Table 2 and, for C. lemniscatus, Vyas et al, 1990) and genetic distances (DNEI, Nei, 1972) based on allozyme electrophoresis (Dessauer and Cole, 1989;Sites et al, 1990) are given for the bisexual species involved in the formation of allodiploids. In some cases, these allodiploids subsequently hybridized with males to produce allotriploid lineages.…”

“…This observation suggests that each of the extant parthenogenetic lineages arose recently from one to a few closely related females (Densmore et al, 1 989a;Moritz et al, 1989a;Vyas et al, 1990).…”

“…Approximately one-third of the species within the genus Cnemidophorus (whiptail lizards), are parthenogenetic and all have arisen through hybridization between bisexual species (Wright, 1978;Dessauer and Cole, 1989;Sites et al, 1990). Previous studies of mtDNA in the parthenogens and their bisexual relatives (Brown and Wright, 1979;Wright et al, 1983;Densmore et al, 1 989a, 1989b;Moritz et al, 1989b;Vyas et al, 1990) have identified the species or subspecies that provided the maternal parent(s) of the initial hybrids, in some cases providing strong evidence for hybrid origins.…”

Incongruence Between Morphological and Mitochondrial-DNA Characters Suggests Hybrid Origins of Parthenogenetic Weevil Lineages (Genus Aramigus)

“…Ð M olecular-phylogenetic studies of parthenogenetic lizards (and other unisexual vertebrates) have largely corroborated the standard model, ® nding generally low divergences between mtDNAs of extant partheno genetic and sexual lineages, and often ® nding polyphy ly of parthenogenetic taxa (Vyas et al, 1990;Avise et al, 1992;M oritz et al, 1992a, 1992bM oritz, 1993). T he iden-ti® cation of still-ex tant maternal and paternal sexual species (and often particular extant source populations) for almost every lineage of parthenogenetic lizards in recent years has been a remarkable success story in the annals of histo rical biology (Dawley and Bogart, 1989;Sites et al, 1990;Cole et al, 1993;Avise, 1994;Cole et al, 1995).…”

An ancient clonal lineage in the fish genus Poeciliopsis (Atheriniformes: Poeciliidae).

“…However, incomplete sampling of the sexual ancestors and incomplete assessment of diversity in the unisexual populations often defeat attempts to discriminate multiple origins from postformation processes. For example, unisexual lineages often are marked by unique alleles not observed in samples of their sexual relatives (7)(8)(9)(10)(11). Although unique alleles might represent postformational mutations, most authors interpret them as "orphan alleles," variants that exist in unsampled sexual populations or that might have existed in extinct sexual progenitors (12).…”