Allen's rule revisited: quantitative genetics of extremity length in the common frog along a latitudinal gradient

Ecogeographical rules linking climate to morphology have gained renewed interest because of climate change. Yet few studies have evaluated to what extent geographical trends ascribed to these rules have a genetic, rather than environmentally determined, basis. This applies especially to Allen's rule, which states that the relative extremity length decreases with increasing latitude. We studied leg length in the common frog (Rana temporaria) along a 1500 km latitudinal gradient utilizing wild and common garden data. In the wild, the body size-corrected femur and tibia lengths did not conform to Allen's rule but peaked at mid-latitudes. However, the ratio of femur to tibia length increased in the north, and the common garden data revealed a genetic cline consistent with Allen's rule in some trait and treatment combinations. While selection may have shortened the leg length in the north, the genetic trend seems to be partially masked by environmental effects.     

Another chloromyxid lineage: molecular phylogeny and redescription of Chloromyxum careni from the Asian horned frog Megophrys nasuta

Infection with Chloromyxum careni Mutschmann, 1999 was found in the Asian horned frog Megophrys nasuta from Malaysia and Indonesia. Kidney was the only organ infected. Coelozoic plasmodia up to 300 μm were localized in Bowman's space, embracing the glomerulus from all sides, or rarely in lumina of renal tubules. Plasmodia are polysporic, containing disporic pansporoblasts. Myxospores observed by light microscopy are colorless, variable in shape and size, measuring 6.0-8.5 × 5.0-6.5 μm, composed of two symmetrical valves joined by a meridian suture, containing four pyriform polar capsules 3.0-4.0 × 2.5-3.0 μm and a single sporoplasm. Each valve possesses 14-24 (median 21) fine longitudinal ridges clearly visible only in scanning electron microscopy. Rarely, atypical spores with a markedly pointed posterior pole and only 6-10 surface ridges are present in plasmodia together with typical spores. Both small subunit (SSU) and large subunit (LSU) rRNA gene sequences possess extremely long GU-rich inserts. In all SSU and LSU rDNA-based phylogenetic analyses, C. careni clustered as a distinct basal branch to the Myxobolus+Myxidium lieberkuehni clade, out of the marine Chloromyxum clade containing Chloromyxum leydigi, the type species of the genus. These morphological and phylogenetic data suggest erection of a new genus for the C. careni lineage, but we conservatively treat it as a Chloromyxum sensu lato until more information is available.     

Genetic divergence and evolutionary relationships in six species of genera Hoplobatrachus and Euphlyctis (Amphibia: Anura) from Bangladesh and other Asian countries revealed by mitochondrial gene sequences

To elucidate the species composition, genetic divergence, evolutionary relationships, and divergence time of Hoplobatrachus and Euphlyctis frogs (subfamily Dicroglossinae, family Ranidae) in Bangladesh and other Asian countries, we analyzed the mitochondrial Cyt b, 12S, and 16S rRNA genes of 252 specimens. Our phylogenetic analyses showed 13 major clades corresponding to several cryptic species as well as to nominal species in the two genera. The results suggested monophyly of Asian Hoplobatrachus species, but the position of African Hoplobatrachus occipitalis was not clarified. Nucleotide divergence and phylogenetic data suggested the presence of allopatric cryptic species allied to Euphlyctis hexadactylus in Sundarban, Bangladesh and several parapatric cryptic species in the Western Ghats, India. The presence of at least two allopatric cryptic species among diverged Euphlyctis cyanophlyctis in Bangladesh, India, and Sri Lanka was also suggested. In some cases, our estimated divergence times matched the paleogeological events of South and Southeast Asian regions that may have led to the divergence of Hoplobatrachus and Euphlyctis taxa. Especially, land formation at Bangladesh (15–10 Ma) may have allowed the spread of these frog taxa to Southeast Asian areas, and the aridification of central India (5.1–1.6 Ma) might have affected the gene flow of widely distributed species. The present study revealed prior underestimation of the richness of the amphibian fauna in this region, indicating the possible occurrence of many cryptic species among these groups.     

All grown‐up and nowhere to go: paedomorphosis and local adaptation in Ambystoma salamanders in the Cuenca Oriental of Mexico

Facultative or obligate paedomorphosis has evolved several times in Mexican populations of the salamander genus Ambystoma, leading to increased genetic divergence among populations with alternate life histories and contributing to population divergence in this species complex. In the present study, we surveyed the genetic diversity of Ambystoma populations in lakes of the Cuenca Oriental, a high elevation closed drainage basin that encompasses permanent crater lakes harbouring salamander populations. We genotyped individuals from five populations aiming to better understand population dynamics and the evolution of paedomorphosis in this system. Specifically, we tested the hypotheses that the evolution of paedomorphosis in Ambystoma taylori resulted in reduced genetic exchange with populations of Ambystoma velasci in neighbouring lakes. Second, we tested whether the populations in brackish lakes of the Cuenca Oriental, Lake Atexcac, and Lake Alchichica show restricted gene flow across the basin, possibly as a result of local adaptation to those microhabitats. Using various indices of population genetic diversity, Bayesian assignment, and approximate Bayesian computation methods, we show that genetic exchange between brackish lakes and freshwater lakes is negligible, despite continued gene flow among freshwater lakes. We show that the first divergence among populations occurred between Alchichica and the remaining populations and that the evolution of paedomorphosis in A. taylori was likely favoured by local adaptation to saline conditions, thus increasing its genetic isolation. An apparently similar process appears to be in progress independently in lake Atexcac, showing that local adaptation may play an important role in population isolation and, ultimately, in speciation.     

Mineralized dermal layer of the Brazilian tree-frog Corythomantis greeningi

Some species of anuran amphibians possess a calcified dermal layer (the Eberth-Kastschenko layer) located between the "stratum spongiosum" and the "stratum compactum." This layer consists of calcium phosphate deposits, proteoglycans, and glycosaminoglycans. Although regarded as a protective layer against desiccation, a calcium reservoir, or possibly a remnant of a dermal skeleton present in anuran ancestors, very little is known about its origin, structure, and function. Thus, we studied the structure and composition of the mineralized dermal layer of Corythomantis greeningi, a peculiar hylid from the Brazilian semiarid region (caatinga), using conventional and cryosubstitution methods combined with transmission, scanning, and analytical electron microscopy. Results show that the dermal layer consists of dense, closely juxtaposed, globular structures. Although the electron opacity of the globules was variable, depending on the type of preparation, crystal-like inclusions were present in all of them, as confirmed by dark field microscopy. Electron probe X-ray microanalysis showed calcium, phosphorus, and oxygen, and electron diffraction revealed a crystalline structure comparable to that of a hydroxyapatite.     

中国西北地区中国林蛙各居群的分类学研究(两栖纲:蛙科)

采用形态学比较和数值分类相结合,对中国西北部分布地中国林蛙Ｒａｎａ ｃｈｅｎｓｉｎｅｎｓｉｓ各居群间（包括分布于青藏庙的地区的原定种或亚种）的差差水平进行了探讨。结果认为：分布于中国西北部高原地区的各居群其形态特征和数值分析这〖其中包括原定名为Ｒａｎａ ａｍｕｒｅｎｓｉｓ ｋｕｋｕｎｏｒｉｓ（Ｎｉｋｏｌ ｓｋｉｉ,１９１８,青海湖）,Ｒ．ｗｅｉｇｏｌｉｄ（Ｖｏｇｔ,１９２４,四川甘孜和德格）,Ｒ．     

中国角蟾属一新种(两栖纲:锄足蟾科)

采自贵州省水城县凤凰乡的一种大形角蟾,因其外部形态与角蟾属Ｍｅｇｏｐｈｒｙｓ已知种有一些特异之处,尤其是鼓膜显露;上颌内缘无栉齿状突;头后部有由痣粒组成的“Ｖ”形棕褐色斑;背部痣纹呈“＊”形;有犁骨棱;雄性无声囊等特征与大花角蟾Ｍ．ｇｉｇａｎｔｉｃａ明显不同。据此认为该角蟾为一新种,定名水城角蟾Ｍｅｇｏｐｈｒｙｓ ｓｈｕｉｃｈｅｎｇｅｎｓｉｓ Ｔｉａｎ,Ｇｕ ｅｔ Ｓｕｎ,ｓｐ．ｎｏｖ．。     

Species diversity of Amphibia, Reptilia and Lipotyphla (Mammalia) at Ambolokopatrika, a rainforest between the Anjanaharibe-Sud and Marojejy massifs, NE Madagascar

The Réserve Spéciale d' Anjanaharibe-Sud and the Parc National de Marojejy are two important areas of biodiversity and endemicity in northeastern Madagascar. These reserves are separated by about 40 km, including the extensive Andapa Basin, and connected by a rather narrow mid-altitude montane ridge. Nothing was previously known about the biota of this corridor and its faunal relations with the two reserves. At this purpose, during 1997 the Ambolokopatrika rainforest (lying about midway between Anjanaharibe-Sud and Marojejy massifs) was surveyed for amphibians, reptiles, and for small mammals belonging to the order Lipotyphla. As a general rule these vertebrates may be important ecological indicators, while the herpetofauna (Amphibia, Reptilia) exhibits a high degree of habitat specialisation and endemicity. Furthermore, the herpetofauna and lipotyphlans of Ambolokopatrika Forest were compared to those known from the forests of Anjanaharibe-Sud, Marojejy, and Tsararano massifs, the latter site being a southern extension of the Anjanaharibe-Sud chain. These animals were surveyed by use of opportunistic searching and pitfall trapping during two seasonal periods, May–June (winter), and November–December (summer). Forty-two species of amphibians, 23 of reptiles, and nine of lipotyphlans were recorded at Ambolokopatrika Forest. The biodiversity of Ambolokopatrika is comparable to those of other analysed sites, and this stresses the value of this forest in assuring biotic exchange between Anjanaharibe-Sud and Marojejy reserves. Considerations are also provided on the faunal similarities and differences in terms of exclusivity and endemisms. It is therefore suggested that a certain degree of protection should be given to Ambolokopatrika rainforest, to assure a biological connection and exchange between the protected areas of Anjanaharibe-Sud and Marojejy.     

Genetic subdivision, glacial refugia and postglacial recolonization in the golden-striped salamander, Chioglossa lusitanica (Amphibia: urodela)

The golden-striped salamander (Chioglossa lusitanica) is an ecologically specialized species, endemic to north-western Iberia. Patterns of genetic variation were assessed at seven polymorphic enzyme loci and one mitochondrial DNA (mtDNA) marker (cytochrome b) in 17 populations across its range. Estimates of enzyme genetic diversity revealed a high degree of genetic subdivision (FST = 0.68), mainly attributable to the existence of two groups of populations. The groups were located, respectively, north and south of the Mondego River, indicating that this river coincided with a major historical barrier to gene flow. A significant decrease in genetic variability from the Mondego northwards was associated with the Douro and Minho rivers. mtDNA sequence variation revealed a congruent pattern of two haplotype groups (d = 2.2%), with a geographical distribution resembling that of allozymes. The pattern and depth of genetic variation is consistent with the following hypotheses: (i) subdivision of an ancestral range of the species prior to the middle Pleistocene; (ii) secondary contact between populations representing historical refugia; (iii) relatively recent range expansion giving rise to the northern part of the species range; and (iv) loss of genetic variation through founder effects during range expansion across major rivers.     

Spermatozoa of Pseudinae (Amphibia, Anura, Hylidae), with a test of the hypothesis that sperm ultrastructure correlates with reproductive modes in anurans

We describe, for the first time, the sperm ultrastructure of the two genera of Pseudinae. Based on sperm ultrastructure, the five species herein examined can be separated into three groups: one containing Pseudis paradoxa, P. bolbodactyla, and P. tocantins, the second containing P. minuta, and the third containing Lysapsus laevis. The midpiece is similar in all species and auxiliary fibers and the undulating membrane are absent. In Pseudis a subacrosomal cone and a multilaminar structure (P. minuta) or a granular material (P. paradoxa group) are seen above the nucleus. Lysapsus laevis has only remnants of the subacrosomal cone. All species have peripheral fibers associated with the outer doublets of the axoneme. We tested the hypothesis of correlation between the presence of an undulating membrane and fertilization environments in anurans using a concentrated changes test (CCT) based on the Hay et al. (Mol Biol Evol 1995;12:928-937) hypothesis of phylogenetic relationships among anuran families. Only a subset of the resolved topologies derived from the Hay et al. (1995) cladogram, where Ranoidea is the sister-group of Sooglossidae, produced significant probabilities of the CCT. Therefore, support for the correlation between sperm ultrastructure and fertilization environments in anurans is, at best, equivocal.