Norma L. Manríquez-Morán

Genetic Variation and Origin of Parthenogenesis in the Aspidoscelis cozumela Complex: Evidence from Mitochondrial Genes

Parthenogenesis is a form of clonal reproduction. Eggs develop in the absence of sperm and offspring are genetically identical to their mother. Although common in invertebrates, it occurs in only a few species of squamate reptiles. Parthenogenetic reptiles have their origin in interspecific hybridization, and their populations are exclusively female. Because of its high mutation rate and maternal inheritance, mitochondrial DNA sequence data can evaluate the origin and evolution of all-female vertebrates. Partial sequences from two mitochondrial genes, Cytb and ND4, were analyzed to investigate questions about the origin of parthenogenesis in the Aspidoscelis cozumela complex, which includes A. cozumela, A. maslini and A. rodecki. Low levels of divergence were detected among parthenogenetic species, and between them and A. angusticeps, confirming it as the maternal species of the parthenoforms. A gene tree was constructed using sequences from three populations of A. angusticeps and nine of its unisexual daughter species. The phylogeny suggests that two independent hybridization events between A. angusticeps and A. deppii formed three unisexual species. One hybridization resulted in A. rodecki and the other formed A. maslini and A. cozumela. Although A. cozumela has the haplotype characteristic of A. maslini from Puerto Morelos, it is considered to be a different species based on karyological and morphological characteristics and its geographical isolation.

REPRODUCTIVE BIOLOGY OF THE PARTHENOGENETIC LIZARD, ASPIDOSCELIS COZUMELA

The reproductive biology of the parthenogenetic lizard Aspidoscelis cozumela was studied from November 1994 to October 1995 on Cozumel Island, Quintana Roo, Mexico. Females exhibit a seasonal pattern with maximum reproductive activity during spring and summer (March to August) associated with day length. Clutch size averaged 1.8 (range 1–4) and was positively correlated with female body size. Females produced at least two clutches within the reproductive season.

Reproductive Activity in Females of the Oviparous Lizard Sceloporus aeneus

Abstract We studied the reproductive cycle of female Sceloporus aeneus from a population southeast of Mexico City (Milpa Alta), Mexico, from April 1993–March 1994. Females have a seasonal reproductive pattern with maximum activity in spring, a pattern typical of temperate oviparous species of the genus. Each female produces up to two clutches per breeding season, with a clutch size ranging from 4–10, which is not correlated with snout-vent length of females. Resumen De abril de 1993 a marzo de 1994 estudiamos el ciclo reproductor de las hembras de Sceloporus aeneus en una población al sureste de la Ciudad de México (Milpa Alta), México. Las hembras muestran un patrón reproductor estacional con actividad máxima en la primavera, un patrón típico de las especies ovíparas de ambiente templado del género. Cada hembra produce hasta dos nidadas por temporada reproductora, con un tamaño de puesta que varía de 4–10 huevos, el cual no se correlaciona con la longitud hocico-cloaca de las hembras.

Seasonal Breeding in the Western Mexican Whiptail Lizard Aspidoscelis costata on Isla Isabel, Nayarit, Mexico

Abstract Timing of sexual activity by males and females is a critical aspect of mating systems. We analyzed whether reproduction in western Mexican whiptail lizards, Aspidoscelis costata, on a tropical Pacific island in Mexico is seasonal or continuous, and whether it is linked to certain meteorological factors. Macroscopic and microscopic analyses of monthly samples of gonads showed that reproductive cycles of males and females were seasonal (February–September) and significantly associated with day length. Necropsies did not evidence an overlap between successive reproductive events in females. However, our observations of free-ranging females showed that 35% of them were accompanied by males >1 time/season, with intervals between accompaniments of 14–31 days. In addition, observations of captive females and males revealed that accompaniment lasted 2–5 days, seemingly coincided with female receptivity and was broken 8–12 days before egg-laying. Repeated accompaniment by males suggests females have successive reproductive events within a season.

Phylogenetic Affinities of the Rare and Enigmatic Limb-Reduced Anelytropsis (Reptilia: Squamata) as Inferred with Mitochondrial 16S rRNA Sequence Data

Abstract The phylogenetic placement of the limbless lizard genus Anelytropsis within Squamata was investigated using partial mitochondrial 16S rRNA sequences (422 bp). A total of 30 species, representing most of the major currently recognized squamate clades, was included in the analysis. As in previous morphological studies, Anelytropsis was strongly supported in Bayesian (mixture and unpartitioned models) and maximum-likelihood analyses as the sister taxon of Dibamus. Thus, a monophyletic Dibamidae composed of these two genera is supported by molecular data for the first time. Furthermore, several relationships in the inferred tree, although weakly supported, were congruent with those found in previous molecular phylogenetic analyses. Among these, Gekkota and the Dibamidae were recovered as relatively basal groups within Squamata. A nonmonophyletic Scleroglossa and Lacertiformes (= Amphisbaenia + Lacertidae + Teiidae + Gymnophthalmidae) also were recovered. Although only weakly supported, a major difference from other recent molecular studies is the basal position of Serpentes.

Integrative species delimitation in practice: Revealing cryptic lineages within the short-nosed skink Plestiodon brevirostris (Squamata: Scincidae)

Integrative taxonomy has been generally considered as a goal in systematics for more than a decade. Here, we employed environmental, molecular, and morphological data to evaluate the species boundaries within the short-nosed skink Plestiodon brevirostris from south-central Mexico, one member of the morphologically conservative P. brevirostris group. Our molecular dataset includes one mitochondrial and two nuclear loci. The mitochondrial fragment includes the full length of the gene coding for the NADH dehydrogenase subunit 1 protein, a segment of the gene coding for 16S ribosomal RNA, and flanking tRNAs. The nuclear dataset includes fragments of the genes coding for the megakaryoblastic leukemia 1 and RNA fingerprint 35 proteins. We employed phylogenetic reconstruction, analyses of population structure and morphological variation, and species delimitation methods (including the integration of the three kinds of data in a unified probabilistic framework) to evaluate species limits. Our results suggest that P. brevirostris represents four distinct species. The information provided by each kind of data allowed us to discern between alternative explanations for the observed patterns of geographic structure. Two of the newly recognized lineages are poorly differentiated morphologically but apparently differ in environmental preferences and are allopatric. Additionally, one lineage is microendemic and parapatric with respect to another one. Moreover, our phylogenetic analyses suggest that other taxa within the P. brevirostris group may represent species complexes. We discuss our results in the context of integrative species delimitation.

Relative importance of reproductive life-history paths in one population of the lizard Sceloporus grammicus

Life cycles of living organisms are composed of distinct sub-cycles that represent alternative life-history paths with differential impact on fitness. We identified three reproductive life-history paths (referred here as loops) in the life cycle of one population of the viviparous lizard Sceloporus grammicus .W e evaluated the relative importance of each one of these reproductive paths for the population fitness of these lizards during a 5-year period. The first path corresponded to early reproduction and included survival to maturity and early fecundity. The second path was late reproduction loop and included survival to larger adult sizes with the corresponding fecundity rate. The third was composed of those individuals skipping the small adult stage within a single year, reaching larger sizes early in life with their corresponding larger litters (fast growth loop). To examine the potential effects of environmental factors on the relative contribution of these alternative life-history paths to fitness, we estimated stage-specific survival and growth as functions of annual temperature and rainfall. Using these estimates of vital rates we constructed annual population projection matrices. Then, using demographic elasticities and loop analysis, we calculated the relative contribution of each of the three reproductive paths to the population growth rates. Our results showed that the early reproduction loop is the path with the greatest relative contribution to the population growth rate in most years. However, increases in environmental temperature resulted in higher population growth rates and in greater contribution of the fast growth path to the overall fitness of these lizards.