Trip Lamb

Phylogenetic relationships of southern African geckos in the Pachydactylus group (Squamata: Gekkonidae)

Abstract Pachydactylus and its close relatives (Chondrodactylus, Colopus, Palmatogecko) constitute the most species‐rich component of the southern African gekkonid fauna. We conducted a phylogenetic analysis of mitochondrial (cytb, 12S rRNA, 16S rRNA) and nuclear (RAG‐1) gene sequences for these geckos. Pachydactylus tetensis + P. tuberculosus form the sister group to the remaining taxa, and we resurrect the genus Elasmodactylus to accommodate these two basal species. The P. bibronii group is sister to Chondrodactylus angulifer, and is here transferred to the latter genus. Pachydactylus kochii is the sister species of Colopus wahlbergii and is transferred to that genus. All remaining taxa ‐ including the P. namaquensis group, the ‘small‐bodied’ Pachydactylus, and Palmatogecko ‐ form a well‐supported monophyletic assemblage recognised herein as Pachydactylus sensu stricto. The major clades within Pachydactylus s.s. include the capensis, serval/weberi, rangei, rugosus, and geitje groups, as well as a diverse “northwestern group” that occurs chiefly in northern Namibia and southern Angola. The fine‐scale regional endemism apparent among members of the southern African Pachydactylus Group probably reflects an interplay between substrate specialisation and vicariant events (both geologically and climatically associated) since at least the Miocene. Explicit phylogenies for Pachydactylus, cordylid lizards, scorpions, and other taxa provide a basis for the first fine‐scaled analytical biogeographic analysis of southern Africa.

MORPHOLOGICAL VARIABILITY IN GENETICALLY DEFINED CATEGORIES OF ANURAN HYBRIDS

Hybridization phenomena in anurans have traditionally been studied through morphological comparisons, under the assumption that various hybrids (e.g., F1‘s, backcrosses) are predictably intermediate to parental species. We critically evaluate this assumption by examining morphology in genetically categorized hybrids between the treefrogs Hyla cinerea and H. gratiosa. A total of 202 frogs from a hybridizing population in Alabama were assayed for allozyme and mitochondrial DNA genotype and for a large suite of osteological characters. Discriminant analyses demonstrated distinct morphological separation between the genetically “pure” parental species. Morphometric analyses of genetically identified hybrids showed: 1) an extreme range of phenotypic expression within F1 and backcross classes, and 2) no apparent directional parental bias on the F1 phenotype. Had morphology alone been used as a guide, over 40 percent of the individuals with known hybrid ancestry would have been misclassified as “pure” parental species, and about 25 percent of the backcross individuals would not have been distinguished from F1‘s. These results exemplify the utility of joint comparisons of morphology and genotypic constitution in studies of natural hybridization, and they emphasize the limitations inherent in describing hybrid classes solely by morphological criteria.

Relationships of the Pachydactylus rugosus group of geckos (Reptilia: Squamata: Gekkonidae)

We examined phylogenetic relationships of the Pachydactylus rugosus complex using DNA sequence data from segments of the mitochondrial genes cytochrome b and 16S ribosomal RNA. These molecular data support the contention that members of the rugosus complex, as defined by McLachlan (1979), form a monophyletic group. Further, high levels of sequence divergence observed between currently recognized subspecies (19.1–26.8 % for cytb), even across short geographic distances, support elevation of each member to full specific rank. The pattern of relationship within the P. rugosus complex species is P. rugosus (P. barnardi, P. formosus). Sequence data provide no evidence to support a close relationship between these taxa and P. capensis, to which previous workers had assigned both P. formosus and P. barnardi.

Genetic and morphometric assessment of an unusual tortoise (Gopherus agassizii) population in the Black Mountains of Arizona

Under recent regulatory designation of the U.S. Fish and Wildlife Service, desert tortoises (Gopherus agassizii) occurring east and south of the Colorado River constitute the Sonoran population, whereas those to the west and north form the Mojave population. These management units, distinguished by significant genetic, morphometric, and ecological differences, represent deep phylogenetic subdivisions within G. agassizii and are of high conservation value. We provide genetic and morphological profiles for an unusual tortoise population inhabiting the Black Mountains of Arizona, some 40 km east of the Colorado River. Both mitochondrial (mt) DNA and morphometric analyses revealed predominately Mojavean features: ten of eleven Black Mountain tortoises possessed Mojave mtDNA markers, and 24 of 37 animals exhibited Mojave morphometric phenotypes. Our results indicate west-to-east movement of tortoises across the Col- orado River, though how or when a Mojave lineage became established in the Black Mountains is difficult to ascertain. Active dispersal, river meander, and human transport (early or modem peoples) serve as plau- sible explanations. Future management of the Black Mountain tortoises should emphasize the populations Mojavean affinities.

Dusky salamanders (Desmognathus, Plethodontidae) from the Coastal Plain: Multiple independent lineages and their bearing on the molecular phylogeny of the genus

Recent phylogenetic reassessment of the lungless salamanders (Plethodontidae) confirmed a major life-history reversal-from direct development to an aquatic larval stage-in the dusky salamanders (Desmognathus) of eastern North America. This reversal initiated high rates of lineage accumulation, reputedly generating the species richness and ecological breath that now characterize Desmognathus. Certain important aspects of the radiation, e.g., ecomorphological evolution, have been identified through intense sampling effort of Appalachian Highland lineages. However, the research preoccupation on montane species has left overlooked a significant component of dusky salamander distribution-the Coastal Plain. We present the first molecular phylogeny for Desmognathus to incorporate extensive coverage from the Atlantic and Gulf coastal plains. We examined 38 Coastal Plain populations in conjunction with 45 additional populations, representing 16 of the 19 nominal species. Bayesian analysis of 88 mitochondrial cox1 haplotypes diagnosed eight independent population lineages within the Coastal Plain, a number at odds with the regions three currently recognized species. Desmognathus has apparently experienced a complex biogeographic history in this physiographic region, one involving multiple invasions and several ecological transitions from lotic to lentic habitats.

CALLING BEHAVIOR AND DIRECTIONAL HYBRIDIZATION BETWEEN TWO TOADS (BUFO MICROSCAPHUS X B. WOODHOUSII) IN ARIZONA

Abstract Male calling effort and mitochondrial DNA (mtDNA) variation were examined in a breeding chorus of toads from a hybrid zone between Bufo microscaphus and B. woodhousii in central Arizona. The chorus comprised 50 B. microscaphus and 17 hybrids, identified on the basis of morphology and advertisement calls; no pure B. woodhousii were observed. Males produced advertisement calls throughout the early evening, even when relatively large numbers of males (>50) were present at the chorus; active searching and satellite tactics were not observed. Calling efforts (call duration × call rate) of hybrids (23.9%, n = 8) and B. microscaphus (24.9%, n = 19) were similar and comparable to call efforts of B. woodhousii (21.9%, n = 10) from a different site. Moreover, repeatabilities of calling effort were significant (r = 0.45) for hybrid males, but not for B. microscaphus and B. woodhousii. Thus, calling behavior of hybrid males was neither significantly reduced nor more variable than that of their parental species. The distribution of mtDNA haplotypes revealed directional introgression is occurring between male B. microscaphus and female B. woodhousii: All 17 hybrids possessed B. woodhousii mtDNA. The proximate mechanism driving hybridization appears to involve common male (B. microscaphus) and rare female (B. woodhousii) matings as B. woodhousii expands its range.

Phylogeographic histories of representative herpetofauna of the southwestern U.S.: mitochondrial DNA variation in the desert iguana (Dipsosaurus dorsalis) and the chuckwalla (Sauromalus obesus)

To determine whether genetic variation in representative reptiles of the southwestern U.S. may have been similarly molded by the geologic history of the lower Colorado River, we examined restriction site polymorphisms in the mitochondrial DNA (mtDNA) of desert iguanas (Dipsosaurus dorsalis) and chuckwallas (Sauromalus obesus). Observed phylogeographic structure in these lizards was compared to that reported for the desert tortoise (Xerobates agassizi), whose mtDNA phylogeny demonstrates a striking genetic break at the Colorado River.

Phylogenetic Relationships of the Large-Bodied Members of the African Lizard Genus Pachydactylus (Reptilia: Gekkonidae)

Abstract Evolutionary relationships among large-bodied species in the gekkonid genus Pachydactylus were investigated using mtDNA sequences from the cytochrome b and 16S ribosomal RNA genes. We combined these data in parsimony and maximum likelihood analyses to address several systematic issues regarding the eight large-bodied taxa, including their phylogenetic position in Pachydactylus as a whole. The large-bodied Pachydactylus do not form a monophyletic group; rather, large size appears to be plesiomorphic. Neither do the large-bodied species exhibiting regional integumentary loss constitute a natural group, as this unusual predator escape mechanism appears in two disparate clades. Both the namaquensis and bibronii groups are monophyletic, the latter being strongly supported. Pachydactylus tuberculosus and Pachydactylus tetensis are consistently basal across analyses, although their phylogenetic position relative to the sister taxon Rhoptropus is uncertain. Equally weighted parsimony recovered a weakly supported Pachydactylus sensu lato (i.e., Pachydactylus + tuberculosus and tetensis), whereas weighted parsimony and maximum likelihood analyses depict tetensis and tuberculosus as taxa sister to Pachydactylus + Rhoptropus. Concordance across all analytical methods lends validity to the synonyms Homodactylus Gray and Elasmodactylus Boulenger, which could be resurrected without compromising the monophyly of the remaining Pachydactylus.

Evolutionary Genetics and Phylogeography of Tassel-Eared Squirrels (Sciurus aberti)

The tassel-eared squirrel ( Sciurus aberti ) is confined to a montane archipelago of mixed conifer forests in the American Southwest. Explanations for its fragmented distribution vary, invoking historical scenarios that stress late-Pleistocene vicariance, dispersal, or some combination thereof. To test among these hypotheses, we examined the phylogeography of S. aberti , as determined by variation in mtDNA restriction sites among 22 populations sampled range-wide. Genetic distance and maximum-parsimony analyses revealed three distinct lineages of mtDNA, which in turn form two major phylogeographic assemblages; eastern (Mexico; New Mexico-Colorado-Utah) and western (Arizona-southwestern New Mexico). Comparisons between the maximum-parsimony tree and an area cladogram of regional mountain ranges showed marked topological discordance, dismissing late-Pleistocene vicariance as a principal phylogeographic factor. Certain mtDNA data support the post-Pleistocene dispersal hypothesis, in which squirrels dispersed northward in conjunction with the rapid range expansion of ponderosa pines ( Pinus ponderosa). However, divergence levels observed between assemblages (1.8%) also suggest a significant, underlying vicariant event responsible for major separation of lineages during the early Pleistocene. Thus, the evolutionary genetics of 5. aberti has been influenced profoundly, and perhaps repeatedly, by climatic change during the Pleistocene.

Morphological asymmetry and interspecific hybridization: A case study using hylid frogs

The limited studies addressing developmental stability of interspecific hybrids suggest a positive association between the level of fluctuating asymmetry and 1) the degree of divergence between parental species, and 2) the recency of the contact zone. To evaluate these associations, we examined asymmetry in a recently‐established hybrid population of treefrogs (Hyla cinerea and H. gratiosa) that show marked structural gene divergence. Fluctuating asymmetry (FA), directional asymmetry, and antisymmetry were assessed for eight paired osteometric traits in allozymically‐defined parental and hybrid categories. FA levels varied considerably among traits. Nonetheless, for any given trait, the hybrid categories did not demonstrate elevated levels of FA compared to the parental categories, or compared to frogs from a non‐hybridizing parental population. The only trait that differed statistically among categories (pterygoid length) involved a significantly lower FA value for the F1 hybrids. Thus, observed FA values do not support expectations that the hybrid categories should experience decreased developmental stability.