四川无尾两栖类的繁殖模式

依据Duellman和Trueb(1986)的定义,对四川无尾两栖动物的繁殖模式多样性进行了研究。研究结果如下:(1)73种四川无尾类可以划分为2类共5种繁殖模式。水内产卵是比较原始的一类繁殖模式,又分2种:静水产卵(模式1)和流水产卵(模式2),68种(93%)是在水内产卵;水外产卵是较进化的一类繁殖模式,又分3种:卵产在近水塘的泥窝中(模式12),卵泡产在近水域的土穴中(模式21)和卵泡产在近水域的树上或灌丛上(模式23),仅5种(7%)在水外产卵。(2)模式1、12、21、23的两栖动物,雌雄性的体型较模式2的物种为小,产卵的数量大,但卵径较小;蝌蚪的生态表型均可归入静水型,共同特点是蝌蚪体型小,在静水中觅食,生长发育快。模式2的两栖动物,雌雄性的体型较大,产卵的数量少,而卵径较大;蝌蚪的生态表型可归入流水型,特点是蝌蚪体型大,在流水中觅食,生长发育慢。(3)水内产卵的两栖动物的窝卵能量投入方式可以分为两种:静水产卵(模式1)的物种通过增加卵的数量来增加投入,接近于r-选择物种;流水产卵(模式2)的物种通过增大卵径来增加投入,接近于k-选择物种;是两种适应不同环境条件的的繁殖策略。     

Mapping amphibian contact zones and phylogeographical break hotspots across the United States

Identifying congruence in the geographical position of lineage breaks and species range limits across multiple taxa is a focus of the field of comparative phylogeography. These regions are biogeographical hotspots for investigations into the processes driving divergence at multiple phylogenetic levels. We used spatially explicit statistical methods to identify these regions for amphibians across the United States. Significant clustering occurred in the Appalachian Mountains and in the general area of Alabama - a region underappreciated as an important amphibian hotspot. When the orders Caudata and Anura were examined separately, spatial clustering was still found in Alabama for both. However, in Caudata the Appalachians and California were also important, and for Anura, the Great Lakes region was highlighted. When species richness was statistically controlled, cluster hotspots shifted out of Alabama and the Appalachians and moved to broader swaths of the Great Lakes region, southwestern United States and California. The exact location of particular suture zones is probably a result of complex interactions between historical and ecological factors including physiography, climate and distance from glacial refugia. These contact zone and phylogeographical break hotspots are ideal arenas in which to test alternative speciation hypotheses and examine the extent of reproductive isolation using novel, integrative approaches combining modern methods in statistical phylogeography, ecological niche modelling and genomics.     

A large-scale phylogeny of Amphibia including over 2800 species, and a revised classification of extant frogs, salamanders, and caecilians

The extant amphibians are one of the most diverse radiations of terrestrial vertebrates (>6800 species). Despite much recent focus on their conservation, diversification, and systematics, no previous phylogeny for the group has contained more than 522 species. However, numerous studies with limited taxon sampling have generated large amounts of partially overlapping sequence data for many species. Here, we combine these data and produce a novel estimate of extant amphibian phylogeny, containing 2871 species (∼40% of the known extant species) from 432 genera (∼85% of the ∼500 currently recognized extant genera). Each sampled species contains up to 12,712 bp from 12 genes (three mitochondrial, nine nuclear), with an average of 2563 bp per species. This data set provides strong support for many groups recognized in previous studies, but it also suggests non-monophyly for several currently recognized families, particularly in hyloid frogs (e.g., Ceratophryidae, Cycloramphidae, Leptodactylidae, Strabomantidae). To correct these and other problems, we provide a revised classification of extant amphibians for taxa traditionally delimited at the family and subfamily levels. This new taxonomy includes several families not recognized in current classifications (e.g., Alsodidae, Batrachylidae, Rhinodermatidae, Odontophrynidae, Telmatobiidae), but which are strongly supported and important for avoiding non-monophyly of current families. Finally, this study provides further evidence that the supermatrix approach provides an effective strategy for inferring large-scale phylogenies using the combined results of previous studies, despite many taxa having extensive missing data.     

Do respiratory metabolic rates of the scyphomedusa Aurelia aurita scale isometrically throughout ontogeny in a sexual generation?

We measured the respiration rate of Aurelia aurita payingspecial attention to the relationship between its metabolic ratesand body mass throughout ontogeny of the jellyfish in a sexualgeneration. Two different regression lines between respirationrates and body dry weight were obtained in ephyra to young medusa(bell diameter 4.2–19 mm, 0.07–14 mg dry weight) and medusa(BD17-120 mm, 12-2100 mg DW), at respective temperatures of 10 and15 °C. The cut off point of the metabolic rates was foundat the developmental stage just being metamorphosed into medusashape (BD 12–20 mm). The slope value of medusa respiration ratewas close to isometric scaling (0.9), whereas that of ephyra toyoung medusa was lower (0.6). Ecological implications of allometricscaling in the early developmental stages of ephyrae and metephyraeare discussed.     

PATTERNS OF POSTZYGOTIC ISOLATION IN FROGS

From literature data on 116 taxa crosses involving 46 species of frogs, we found a positive correlation between degree of divergence (measured as Nei's genetic distance, D) and degree of postzygotic isolation. In anurans, hybrid sterility appears to evolve more quickly than inviability, which is consistent with the conclusions of other studies that involved Drosophila species. The lower threshold of D = 0.30 for evolution of hybrid inviability that we found is similar to that observed for Drosophila. This consistency suggests that there may be a general pattern in the acquisition of reproductive isolation in animals.     

Morphological evolution of Ceratophryinae (Anura, Neobatrachia)

Body form is one of the major consequences of development, and diversification of body shapes implies developmental changes among species. In anurans, changes in the timing of developmental events or heterochrony, have been emphasized as a source of variation in the patterns of development that has lead to diverse morphology. Herein, different approaches are used to explore morphological traits in members of the Ceratophryinae (Anura: Leptodactylidae), a group of frogs with some features produced by overdevelopment. Cladistic analyses were conducted in order to distinguish the shared history of Ceratophrys, Chacophrys and Lepidobatrachus and other anurans. From these studies, morphological variation of selected skeletal features in ceratophryines reveals the presence of ancient structures, which have been considered lost in the neobatrachian phylogeny, integrated in particular designs. Thin-plate spline morphometric analyses of skull shapes among ceratophryines describe Lepidobatrachus as the most distinctive shape. Moreover, thin-plate spline morphometric analyses among anurans show divergent skull shapes between ceratophryines and other anurans, reflecting that the skull shapes of ceratophryines are a result of peramorphosis (increase of developmental rates). This study represents the first detailed examination of the role of peramorphosis in a clade of anurans.