Neglected native or undesirable alien? Resolution of a conservation dilemma concerning the pool frog Rana lessonae

Introduced species often pose serious threats to biodiversity, but occasionally confusion arises as to whether a species really is introduced or is in fact an overlooked native. A recent UK conservation dilemma has centred on the status of the pool frog Rana lessonae. This species has been the subject of documented introductions from central and southern Europe since the early 1800s, the accepted position being that all UK R. lessonae populations are descended from these introductions. However, a closer examination of early UK literature sources, and recent discoveries of isolated, native R. lessonae populations in Sweden and Norway, led some herpetologists to question whether the species was in fact present as a native at some locations prior to the introductions. Research was initiated along four major lines of enquiry: genetic, bioacoustic, archaeozoological and archival. A high degree of convergence among the genetic and bioacoustic investigations demonstrated that the potentially native UK pool frogs were closely related to Scandinavian frogs, thus ruling out introductions from further south as a potential origin. Subfossil evidence of pool frogs was found from ca. 1000 years before present, demonstrating that the species occurred in the UK prior to known introductions. Archival sources produced no historical support for introductions from northern Europe. The postglacial history inferred for these northern populations is consistent with the known climatic and geographical conditions. Taken together, the evidence for the native status of the pool frog is compelling, and furthermore the UK population appears to be part of a distinct northern clade.     

Development and characterization of polymorphic microsatellite DNA loci for the endangered dusky gopher frog,Rana sevosa,and two closely related species,Rana capito and Rana areolata

A microsatellite library was developed using genomic DNA of the endangered dusky gopher frog, Rana sevosa. Polymerase chain reaction (PCR) primers and conditions are presented for R. sevosa (eight loci) and two sister taxa — other gopher frogs, Rana capito (seven loci) and crawfish frogs, Rana areolata (three loci). Polymorphism of each microsatellite locus was evaluated for each species. All loci have moderate to high genetic variation in terms of allelic richness (four to 10 alleles per locus), observed heterozygosity (0.595–0.946), and expected heterozygosity (0.531–0.856).     

浙江丽水虎纹蛙形态特征的两性异形和食性

用数显游标卡尺测量了407只2001—2003年9月下旬至10月上旬浙江丽水罚没的死亡虎纹蛙的体长等10个形态指标,结果表明:雌性成体体长(SUL)大于雄性成体,幼体形态无显著两性差异;ANCOVA去除SUL差异的影响后,雌性成体的头长和后肢长大于雄性成体,前肢长、眼径和耳径则小于雄性成体。前肢两侧对称性的偏移度成体大于幼体,雌性大于雄性;后肢两侧对称性成幼体和两性无显著差异。10个形态指标主成分分析的前三个主成分共解释64·6%的变异:第一主成分中头宽、眼径和耳径,第二主成分中后肢长,第三主成分中眼间距和鼻间距分别有较高的正负载系数。用NikonSMZ-1000解剖镜鉴别277只个体胃内容物中的食物种类,发现其秋季食物以节肢动物为主;成幼体和两性食物生态位宽度为3·42~5·25,食物生态位重叠度较高为0·93~0·98。分析表明,虎纹蛙局部形态特征的两性差异微弱,而体长两性异形差异显著;雌体具有较大的体形与食性无关,而可能与生育力选择的作用有关。     

When a clonal genome finds its way back to a sexual species: evidence from ongoing but rare introgression in the hybridogenetic water frog complex

Besides several exceptions, asexual metazoans are usually viewed as ephemeral sinks for genomes, which become ‘frozen’ in clonal lineages after their emergence from ancestral sexual species. Here, we investigated whether and at what rate the asexuals are able to introgress their genomes back into the parental sexual population, thus more or less importantly affecting the gene pools of sexual species. We focused on hybridogenetic hybrids of western Palaearctic water frogs (Pelophylax esculentus), which originate through hybridization between P. ridibundus and P. lessonae, but transmit only clonal ridibundus genome into their gametes. Although usually mating with P. lessonae, P. esculentus may upon mating with P. ridibundus or another hybrid produce sexually reproducing P. ridibundus offspring with the introgressed ex‐clonal genome. We compared the rate of nuclear amplified fragment length polymorphism (AFLP) and mitochondrial introgression in two types of populations, that is, those where P. ridibundus occurs in isolation and those where it lives with the hybridogens. Although significant differentiation (Φpt) between sexual and clonal ridibundus genomes suggested limited gene flow between sexuals and hybridogens, a non‐negligible (~5%) proportion of P. ridibundus bore introgressed mtDNA and AFLP markers. Whereas transfer of mtDNA was exclusively unidirectional, introgression of nuclear markers was bidirectional. The proportion of introgressed P. ridibundus was highest in syntopic populations with P. esculentus, proving an ongoing and site‐specific interspecific genetic transfer mediated by hybridogenetic hybrids. It turns out that asexual hybrids are not just a sink for genes of sexual species, but may significantly influence the genetic architecture of their sexual counterparts.     

Antimicrobial peptides from the skins of North American frogs

North America is home to anuran species belonging to the families Bufonidae, Eleutherodactylidae, Hylidae, Leiopelmatidae, Ranidae, and Scaphiopodidae but antimicrobial peptides have been identified only in skin secretions and/or skin extracts of frogs belonging to the Leiopelmatidae (“tailed frogs”) and Ranidae (“true frogs”). Eight structurally-related cationic α-helical peptides with broad-spectrum antibacterial activity, termed ascaphins, have been isolated from specimens of Ascaphus truei (Leiopelmatidae) occupying a coastal range. Characterization of orthologous antimicrobial peptides from Ascaphus specimens occupying an inland range supports the proposal that this population should be regarded as a separate species A. montanus. Ascaphin-8 shows potential for development into a therapeutically valuable anti-infective agent. Peptides belonging to the brevinin-1, esculentin-1, esculentin-2, palustrin-1, palustrin-2, ranacyclin, ranatuerin-1, ranatuerin-2, and temporin families have been isolated from North American ranids. It is proposed that “ranalexins” represent brevinin-1 peptides that have undergone a four amino acid residue internal deletion. Current taxonomic recommendations divide North American frogs from the family Ranidae into two genera: Lithobates and Rana. Cladistic analysis based upon the amino acid sequences of the brevinin-1 peptides provides strong support for this assignment.     

我国臭蛙属(两栖纲:蛙科)的系统发育

为探讨臭蛙属的种间亲缘关系与其起源和分化,采用PAUP3．1软件对我国的16种臭蛙的29项分类性状进行系统发育关系的研究。结果表明,臭蛙属物种形成1个单系群,可以划分为4个种组;表明了臭蛙属中国物种间的亲缘关系;无指盘臭蛙和云南臭蛙是本属中最原始的物种,鸭嘴臭蛙等是较特化的物种;原始臭蛙可能起源于横断山区和云南西部高原,贵州高原可能是臭蛙的分化中心;各种组内相近种的地理替代呈南北方向更替,而种组间则呈东西方向更替;原始物种多分布于中国西南部,较进化或特化物种多分布于中国东部和东南部及海岛上;其种组亲缘关系与地理分布格局显示出一致性。     

从12S rRNA基因序列研究中国蛙科24种的进化关系

测定了中国蛙科动物24种和蟾蜍科的中华大蟾蜍线粒体12S rRNA基因长约400bp片段的序列。采用邻接法,对其数据的系统发生分析表明24种可分成3个支系：第一个支系包括棘腹蛙、合江棘蛙、棘胸蛙、大头蛙、虎纹蛙、倭蛙、泽陆蛙共７种,其中３种棘蛙组成一个单系;第二个支系由３种湍蛙,即戴云湍蛙、华南湍蛙和武夷湍蛙组成,应属于湍蛙亚科;第三支系包含余下的１４种蛙,其中５种林蛙和４种臭蛙分别组成一个单系;２种侧褶蛙先聚合后,再与弹琴水蛙聚合,２种粗上先聚合在一起,再与由林蛙组成的单系群聚合。第三支系首先与第二支系相聚,然后它们与第一支系形成姐妹群,即由蛙亚科的７个物种组成的第一支系,不与蛙亚科另１４个物种组成的第三支系直接聚合,表明第一支系的物种可能不属于蛙亚科。此外,分子证据提示把陆蛙属、大头蛙属、虎纹蛙属、棘棘属、臭蛙属、粗皮蛙属和侧褶蛙属从原来的蛙属分出有其合理性。、     

西藏东南部棘蛙属一新种记述(两栖纲：蛙科)

对产于西藏东南部察隅和墨脱的察隅棘蛙通过形态特征和数值分类作了进一步比较研究,结果认为：产于察隅的察隅棘蛙是一个有效种,而产于墨脱的标本应为一个新种,即墨脱棘蛙Paa medogensis sp.nov.。     

Multiple origins of invasive and ‘native’ water frogs (Pelophylax spp.) in Switzerland

The marsh frog (Pelophylax ridibundus) has been introduced in many areas in Central and Western Europe as a result of commercial trade with Eastern Europe, and is rapidly replacing the native pool frog (P. lessonae). A large number of Pelophylax species are distributed in Eastern Europe and the strong phenotypic similarity between these species is rendering their identification hazardous. Consequently, alien populations of Pelophylax might not strictly be composed of P. ridibundus as previously suspected. In the present study, we analysed the cytochrome‐b and NADH dehydrogenase subunit 3 genes of introduced and native Pelophylax species from Switzerland (299 individuals) in order to properly identify the source populations of the invaders and the genetic status of the native species. Our study highlighted the occurrence of several genetic lineages of invasive frogs in western Switzerland. Unexpectedly, we also showed that several populations of the native pool frog (P. lessonae) cluster with the Italian pool frog P. bergeri from central Italy (considered by some authors as a subspecies of P. lessonae). Hence, these populations are probably also the result of introductions, meaning that the number of native P. lessonae populations is fewer than expected in Switzerland. These findings have important implications concerning the conservation of the endemic pool frog populations, as the presence of multiple alien species could strongly affect their long‐term subsistence. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 442–449.     

Morphometric and DNA investigations into European water frogs (Rana kl. esculenta Synklepton (Anura, Ranidae)) from different population systems

The population specific variability of diploid and triploid R. kl. esculenta individuals was investigated by means of morphometric methods (canonical discriminant analysis, UPGMA cluster analysis) and DNA fingerprinting. As a result of the morphometric investigations, as well as of the DNA investigations, a clear separation of single populations was possible. However, no correlations between the morphometry and different population systems could be recognized. Clear morphometric differences could be seen between diploid ♀♀ and ♂♂ and triploid ♀♀ on the one hand, and triploid ♂♂ on the other. While the diploid ♀♀ and ♂♂ and the triploid ♀♀ were located in the intermediate area between the parental species R. lessonae and R. ridibunda according to their morphometric parameters, the triploid ♂♂ showed a great overlap with R. lessonae. Up to now, this phenomenon has not been explained. The first results of the DNA investigations provided further hints at the high inter-individual and population-specific variability of R. kl. esculenta. R. kl. esculenta individuals of the R. lessonae/esculenta population Toter See could be distinguished from conspecific individuals of the R. ridibunda/esculenta-♀♀ population Alte Oder according to their fingerprint patterns. Moreover, in the R. lessonae / esculenta population, the fingerprints or the diploid R. kl. esculenta-♀♀ and the investigated R. lessonae-♀ were very similar. Furthermore, in this population, many R. kl. esculenta genotypes resemble R. lessonae in their morphometric features. This finding suggests the occurrence of recombination in R. kl. esculenta. In general, every population seems to have its own genetic background. A classification of water-frog populations according to population systems is only possible under certain conditions.