Valerio Sbordoni

MOLECULAR BIOGEOGRAPHY OF CAVE LIFE: A STUDY USING MITOCHONDRIAL DNA FROM BATHYSCIINE BEETLES

This study focuses on phylogenetic relationships in two distinct species assemblages of cave‐dwelling beetles with similar disjunct distributions in the Pyrenees and Sardinia. One assemblage contains six species in the genera Ovobathysciola (four species) and Patriziella (two species) on Sardinia and one species of Anillochlamys in the Pyrenees. Species within the two Sardinian genera co‐occur in the same karst area. Although, they are believed to be each others closest relative, they have very different body types (globular body with short appendages in Ovobathysciola; elongated body with long appendages in Patriziella), which are believed to reflect different degrees of adaptation to cave life. The other assemblage of Bathysciine beetles includes three species in the genus Speonomus in the Pyrenees and one on Sardinia. All the species are rare and many are endangered.

Bottleneck effects and the depression of genetic variability in hatchery stocks of Penaeus japonicus (Crustacea, Decapoda)

Aquaculture of Penaeus japonicus is developing in Italy at a production level. Genetic analysis of the founder stock and five subsequent hatchery generations revealed a constant reduction in levels of allozyme polymorphism. Average heterozygosity decreased from 0.102 to 0.039. The magnitude of the reduction in heterozygosity was much higher than expected from the numbers of breeders placed into spawning tanks at each reproductive cycle. We estimated, under the assumption of neutrality, that the effective number of parents contributing to each broodstock might have been as low as four, although the number of shrimp pairs held in spawning tanks varied from 50 to 300 after an initial bottleneck occurred in the first generation. This discrepancy may be explained as the combined effect of some common farming practices and it points out the importance of a careful check of the number of spawners actually contributing to each reproductive cycle.

Molecular biogeography: using the Corsica-Sardinia microplate disjunction to calibrate mitochondrial rDNA evolutionary rates in mountain newts (Euproctus)

Mitochondrial DNA (mtDNA) sequence variation was examined in the three species belonging to the newt genus Euproctus: E. asper, E. montanus, and E. platycephalus, and in three other species belonging to the same family: Triturus carnifex, T. vulgaris and Pleurodeles waltl. The Euproctus species inhabit mountain streams in the Pyrenean region, Corsica, and Sardinia, respectively. This vicariant distribution is believed to be a result of the disjunction and rotation of the Sardinia‐Corsica microplate from the Pyrenean region and suggested dates for each cladogenetic event are available. A total of 915 bp from 12S and 16S ribosomal rRNA genes were compared for each taxon. These are the first mt‐rDNA sequence data for salamanders. Sequences were used to reconstruct phylogenetic trees, investigate evolutionary rates for these genes, calibrate them with absolute time since divergence, and compare rates with published ones.

Pleistocene evolutionary history of the Clouded Apollo (Parnassius mnemosyne): genetic signatures of climate cycles and a 'time-dependent' mitochondrial substitution rate.

Genetic data are currently providing a large amount of new information on past distribution of species and are contributing to a new vision of Pleistocene ice ages. Nonetheless, an increasing number of studies on the ‘time dependency’ of mutation rates suggest that date assessments for evolutionary events of the Pleistocene might be overestimated. We analysed mitochondrial (mt) DNA (COI) sequence variation in 225 Parnassius mnemosyne individuals sampled across central and eastern Europe in order to assess (i) the existence of genetic signatures of Pleistocene climate shifts; and (ii) the timescale of demographic and evolutionary events. Our analyses reveal a phylogeographical pattern markedly influenced by the Pleistocene/Holocene climate shifts. Eastern Alpine and Balkan populations display comparatively high mtDNA diversity, suggesting multiple glacial refugia. On the other hand, three widely distributed and spatially segregated lineages occupy most of northern and eastern Europe, indicating postglacial recolonization from different refugial areas. We show that a conventional ‘phylogenetic’ substitution rate cannot account for the present distribution of genetic variation in this species, and we combine phylogeographical pattern and palaeoecological information in order to determine a suitable intraspecific rate through a Bayesian coalescent approach. We argue that our calibrated ‘time‐dependent’ rate (0.096 substitutions/million years), offers the most convincing time frame for the evolutionary events inferred from sequence data. When scaled by the new rate, estimates of divergence between Balkan and Alpine lineages point to c. 19 000 years before present (last glacial maximum), and parameters of demographic expansion for northern lineages are consistent with postglacial warming (5–11 000 years before present).

Molecular evolutionary divergence among North American cave crickets. I: Allozyme variation

Forty‐nine populations of nine species of North American cave crickets (genera Euhadenoecus and Hadenoecus) have been studied for genetic variation at 41 loci by electrophoresis. Wrights FST, Slatkins Nm* gene‐flow estimator, and Neis genetic distances (D) have been used to compare closely related species that have different ecological requirements (cave vs. forest species), distribution patterns, and/or different degrees of geographic isolation among populations.

Tempo and mode of species diversification in Dolichopoda cave crickets (Orthoptera, Rhaphidophoridae)

This study focuses on the phylogenetic relationships among ninety percent of known Dolichopoda species (44 out of 49); primarily a Mediterranean genus, distributed from eastern Pyrenees to Caucasus. A total of 2490 base pairs were sequenced corresponding to partial sequences of one nuclear (28SrRNA) and three mitochondrial genes (12S, 16S and COI). A relaxed molecular clock, inferred from Bayesian analysis was applied to estimate the divergence times between the lineages using well dated palaeoevents of the study areas. Molecular substitution rates per lineage per million years were also obtained for each analyzed gene. Based on the nearly complete species phylogeny, temporal patterns of diversification were analyzed using Lineage-Through-Time plots and diversification statistics. Alternative hypotheses about the colonization of present range by Dolichopoda species were tested by means of Approximate Bayesian Computation analysis. Results from this analysis carried out on the 90% of known Dolichopoda species confirmed the previous ones based on subgroups of species, suggesting the ABC analysis as a remarkable tool in biogeographic studies. Based on these results, the distribution of Dolichopoda species appears to have been shaped by the palaeogeographic and climatic events that occurred from Late Miocene up to the Plio-Pleistocene. Both vicariance and dispersal events appear to have influenced Dolichopoda species distributions, with many processes occurring in ancestral epigean populations before the invasion of the subterranean environment.

Acclimation of the European sea bass to freshwater: monitoring genetic changes by RAPD polymerase chain reaction to detect DNA polymorphisms

We investigated the use of the polymerase chain reaction (PCR) and the associated random amplification of polymorphic DNA (RAPD) technique to study variation in samples of the sea bass, Dicentrarchus labrax, before and after acclimation to freshwater. Acclimation trials were repeated twice, in 1989 and 1990, for two samples originating from the same broodstock (individuals from different localities along the Italian coasts), with overall mortality rates averaging 94 and 75% in the 2 yr, respectively. Analyses are based on 126 polymorphic RAPD markers, scored in at least 39 individuals for each of the starting and acclimated samples in both years. Analysis of RAPD patterns revealed high levels of DNA polymorphism in both 1989 and 1990 starting samples. The acclimated samples maintained similar polymorphism levels. Shifts in marker frequencies between starting and acclimated samples occurred in both years. A correspondence analysis carried out on multimarker individual profiles suggests that the two starting samples resulted from uneven sampling of the same heterogenous broodstock. This analysis clearly separates RAPD phenotypes from starting and acclimated samples in both years and identifies the RAPD markers responsible for such displacement. Patterns of RAPD variation are compared with previous allozymic studies carried out on the same samples. A major difference between the two studies was the number of markers available. Fewer allozyme loci were studied than were RAPD markers. The cause of repeated shifts for allozyme alleles in replicate experiments were almost certainly due to selection, while statistical chance could explain the repeated shift of only one out of more than 100 RAPD markers. We have shown that RAPD analysis, if carried out carefully, is quite reproducible and sensitive enough to reveal high levels of variation among individuals from the same broodstock. A major drawback of this approach is the still unclear inheritance patterns of RAPD polymorphisms. The use of multivariate analyses is suggested as a possible alternative to traditional population genetics techniques to analyze patterns of variation in the absence of a precise genetic interpretation.

An overlooked pink species of land iguana in the Galápagos

Despite the attention given to them, the Galápagos have not yet finished offering evolutionary novelties. When Darwin visited the Galápagos, he observed both marine (Amblyrhynchus) and land (Conolophus) iguanas but did not encounter a rare pink black-striped land iguana (herein referred to as “rosada,” meaning “pink” in Spanish), which, surprisingly, remained unseen until 1986. Here, we show that substantial genetic isolation exists between the rosada and syntopic yellow forms and that the rosada is basal to extant taxonomically recognized Galápagos land iguanas. The rosada, whose present distribution is a conundrum, is a relict lineage whose origin dates back to a period when at least some of the present-day islands had not yet formed. So far, this species is the only evidence of ancient diversification along the Galápagos land iguana lineage and documents one of the oldest events of divergence ever recorded in the Galápagos. Conservation efforts are needed to prevent this form, identified by us as a good species, from extinction.

Patterns of evolution and multidimensional systematics in graylings (Lepidoptera: Hipparchia)

The difficult and controversial attribution of Hipparchia (Parahipparchia) populations to species or subspecies rank led us to use a comparative, quantitative approach to clarify evolutionary and taxonomic relationships among taxa. Seventeen populations from the Mediterranean area belonging to nine presumptive species or subspecies were sampled, and multivariate analyses were employed to study three character sets: allozymes, morphometric profiles of male genitalia, and quantitative descriptors of wing pattern and shape. Comparative analyses of distance matrices, trees and ordination patterns enabled us to outline evolutionary relationships among taxa and to assess the relative value of each character set. Congruent relationships among taxa were obtained from allozymes and male genital morphometrics, suggesting that divergence in genital morphology is a fairly good marker of the overall genetic divergence. On the other hand, discordant results from wing pattern descriptors suggest these might be subjected to different evolutionary trajectories and rates because of their particular adaptive significance, and might not represent reliable tracers of phylogeny.

Plant sciences and the Italian National Biodiversity Network

Abstract Several national and global initiatives aim to increase access to biodiversity information worldwide. The Italian National Biodiversity Network, started in the framework of the project “Sistema Ambiente 2010”, will organise and manage biodiversity data hosted by museums, universities and research centres in Italy, in order to make them widely available on the Web.