Paolo Colangelo

The Gavialis--Tomistoma debate: the contribution of skull ontogenetic allometry and growth trajectories to the study of crocodylian relationships

SUMMARY The phylogenetic placement of Tomistoma and Gavialis crocodiles depends largely upon whether molecular or morphological data are utilized. Molecular analyses consider them as sister taxa, whereas morphological/paleontological analyses set Gavialis apart from Tomistoma and other crocodylian species. Here skull allometric trajectories of Tomistoma and Gavialis were contrasted with those of two longirostral crocodylian taxa, Crocodylus acutus and Mecistops cataphractus, to examine similarities in growth trajectories in light of this phylogenetic controversy. Entire skull shape and its two main modules, rostrum and postrostrum, were analyzed separately. We tested differences for both multivariate angles between trajectories and for shape differences at early and late stages of development. Based on a multivariate regression of shape data and size, Tomistoma seems to possess a peculiar rate of growth in comparison to the remaining taxa. However, its morphology at both juvenile and adult sizes is always closer to those of Brevirostres crocodylians, for the entire head shape, as well as the shape of the postrostrum and rostrum. By contrast, the allometric trajectory of Gavialis always begins and ends in a unique region of the multidimensional morphospace. These findings concur with a morphological hypothesis that places Gavialis separate from Brevirostres, and Tomistoma closer to other crocodylids, and provides an additional, and independent, data set to inform on this ongoing phylogenetic discussion.

Multiple lines of evidence for demographic and range expansion of a temperate species (Hyla sarda) during the last glaciation

Many temperate species experienced demographic and range contractions in response to climatic changes during Pleistocene glaciations. In this study, we investigate the evolutionary history of the Tyrrhenian tree frog Hyla sarda, a species inhabiting the Corsica–Sardinia island system (Western Mediterranean basin). We used sequence analysis of two mitochondrial (overall 1229 bp) and three nuclear (overall 1692 bp) gene fragments to assess the phylogeography and demographic history of this species, and species distribution modelling (SDM) to predict its range variation over time. Phylogeographic, historical demographic and SDM analyses consistently indicate that H. sarda does not conform to the scenario generally expected for temperate species but rather underwent demographic and range expansion mostly during the last glacial phase. Palaeogeographic data and SDM analyses suggest that such expansion was driven by the glaciation‐induced increase in lowland areas during marine regression. This unusual scenario suggests that at least some temperate species may not have suffered the adverse effects of glacial climate on their population size and range extent, owing to the mitigating effects of other glaciations‐induced palaeoenvironmental changes. We discuss previous clues for the occurrence of such a scenario in other species and some possible challenges with its identification. Early phylogeographic literature suggested that responses to the Pleistocene glacial–interglacial cycles were expected to vary among species and regions. Our results point out that such variation may have been greater than previously thought.

REDUCED GENE FLOW AT PERICENTROMERIC LOCI IN A HYBRID ZONE INVOLVING CHROMOSOMAL RACES OF THE HOUSE MOUSE MUS MUSCULUS DOMESTICUS

The West European house mouse, Mus musculus domesticus, is a particularly suitable model to investigate the role of chromosomal rearrangements in reproductive isolation. In fact, it exhibits a broad range of chromosomal polymorphism due to Robertsonian (Rb) fusions leading to various types of contact zones between different chromosomal races. In the present study, we analyzed a parapatric contact in central Italy between the Cittaducale chromosomal race (CD: 2n= 22) and the surrounding populations with standard karyotype (2n= 40) to understand if Rb fusions play a causative role in speciation. One hundred forty‐seven mice from 17 localities were genotyped by means of 12 microsatellite loci. A telomeric and a pericentromeric locus situated on six chromosome arms (four Rbs and one telocentric) were selected to detect differences in the amount of gene flow for each locus in different chromosomal positions. The analyses performed on the two subsets of loci show differences in the level of gene flow, which is more restricted near the centromeres of Rb chromosomes. This effect is less pronounced in the homozygotes populations settled at the border of the hybrid zone. We discuss the possible cause of the differential porosity of gene flow in Rbs considering “hybrid dysfunctions” and “suppressed recombination” models.

Molecular systematics and evolutionary biogeography of the genus Talpa (Soricomorpha: Talpidae).

The range of the genus Talpa covers almost all Europe up to Western Asia. This genus has never been the object of comprehensive systematic studies using molecular and genetic techniques, such that the evolutionary relationships among species remain unclear. Talpa shows high levels of endemism, and the influence of past glaciation cycles on the distribution pattern of several species has been hypothesized. In this work, we assessed the molecular systematics of the genus using the mitochondrial gene cytochrome b from eight of the nine extant species of Talpa moles. Furthermore, molecular clock estimations were used to hypothesize a biogeographic scenario in concordance with fossil data. Results suggest a monophyletic origin of the genus and a common ancestor for the western European moles T. europaea, T. caeca, T. romana and T. occidentalis. The eastern species T. altaica and T. caucasica are basally divergent. The estimated ages of divergence among lineages are in accordance with a Miocene origin of the extant moles. The genus likely originated in Asia, spreading into Europe during the Pliocene. The evolution of moles appears to have been driven by changes in moisture levels that influenced extinction and speciation events during the Miocene and the Pliocene. Pleistocene climatic oscillations likely caused the range shrinkages and expansions that led to the current distribution pattern of most Talpa species.

Molecular phylogenetics of the genus Gerbillus (Rodentia, Gerbillinae): Implications for systematics, taxonomy and chromosomal evolution.

Although gerbils forms an important component of the mammalian fauna of arid and semi-arid area, the taxonomic and phylogenetic relationship within the species of the genus Gerbillus are still ambiguous. The present paper introduces findings based on the whole cytochrome b (1140 bp) mitochondrial genes of seven species (Gerbillus campestris, G. latastei, G. nanus, G. tarabuli, G. gerbillus, G. simoni and G. nigeriae) six of which are present in Tunisia. Our results show that all the Gerbillus species are monophyletic. Moreover, molecular phylogeny rejects the genus rank for the taxon Dipodillus. Gebillus nanus, a species belonging to the subgenus Hendecapleura, early diverged from the other species which are divided into two clades: the subgenus Dipodillus, including G. campestris and G. simoni and the subgenus Gerbillus including G. gerbillus, G. nigeriae, G. tarabuli and G. latastei. These results are congruent with morphological and karyological evidences. According to molecular clock, the appearance of the genus Gerbillus coincides with the Miocene-Pliocene expansion of African arid biomes. Extensive intraspecific chromosomal changes evolved in a relatively narrow lapse of time, like in the case of G. latastei, allowing the fixations of different chromosomal variants due to pericentric inversion.

The Rodent fauna of Tanzania : a cytotaxonomic report from the Maasai Steppe

The rodent fauna of Tanzanian savannahs is poorly known. For this reason, the Accademia Nazionale dei Lincei sponsored a project together with the Biology Department of Antwerp and the Sokoine University of Agriculture (Morogoro, Tanzania) on Eastern African rodents. The aim was to study the taxonomy and systematics of rodents of these areas and the processes through which rodent biodiversity has increased in these African regions. We present here a report of the expeditions carried out in the Maasai steppe of Tanzania during 1999, with the description of the karyotypes of 13 rodent species. These are:Saccostomus cf.mearnsi (Cricetomynae),Tatera cf.robusta, Gerbillus cf.pusillus (Gerbillinae),Acomys spinosissimus, Acomys wilsoni, Acomys ignitus, Aethomys cf.chrysophilus, Arvicanthis cf.neumanni, Arvicanthis cf.nairobae, Grammomys sp.,Lemniscomys rosalia, Lemniscomys cf.zebra, Mastomys natalensis (Murinae). The karyotypes of eight species are described for the first time (Saccostomus cf.mearnsi, Gerbillus cf.pusillus, Acomys wilsoni, Acomys ignitus, Arvicanthis cf.neumanni, Arvicanthis cf.nairobae, Grammomys sp.,Lemniscomys rosalia).RiassuntoLa fauna a roditori della Tanzania è scarsamente conosciuta; per questo motivo l’Accademia Nazionale dei Lincei ha finanziato, assieme al Dipartimento di Biologia di Anversa (Belgio) e al Dipartimento di Agronomia della Sokoine University di Morogoro (Tanzania), un progetto inteso, d’un lato, a chiarire la tassonomia e la sistematica dei roditori di questa area, e, dall’altro, a studiare i processi attraverso i quali viene incrementata la biodiversità di questa regione africana. In questo rapporto si riferiscono i risultati delle spedizioni effettuate in Tanzania nel 1999 nella Steppa dei Masai, con la descrizione del cariotipo di 13 specie di roditori: 1 Cricetomynae,Saccostomus cfr.mearnsi, 2 Gerbillinae,Tatera cfr.robusta, Gerbillus cfr.pusillus, e 10 Murinae,Acomys spinosissimus, Acomys wilsoni, Acomys ignitus, Aethomys cfr.chrysophilus, Arvicanthis cfr.nairobae, Arvicanthis cfr.neumanni, Grammomys sp.,Lemniscomys cfr.zebra, Lemniscomys rosalia, Mastomys natalensis. Otto cariotipi risultano descritti per la prima volta e sono stati messi in evidenza casi di polimorfismo e/o politipismo.

Origin and evolution of Western European moles (genus Talpa, Insectivora): a multidisciplinary approach

ABSTRACT The European representatives of the subfamily Talpinae belong to the monophyletic genus Talpa. Five out of the nine species of Talpa occur in Western Europe. A wide central area is occupied by Talpa europaea, while the small sized Talpa caeca occurs in southern Europe. Three endemic species are restricted to the peripheral areas of the genus range and show a parapatric distribution with respect to T. europaea, i.e. the Iberian T. occidentalis, the southern Italian T. romana and the Balkan T. stankovici. The karyotypes of moles are very conservative, with the majority of the species showing 2n = 34. Allozyme data first allowed to assess the specific status of endemic taxa and the low levels of heterozygosity. Neis genetic distances suggest that T. occidentalis, T. romana and T. stankovici early diverged from an europaea–caeca line. Preliminary results from mtDNA analyses strongly support the monophyly of Western European moles, but are still not able to solve the relationships within this clade. Estimates of time of divergences indicate a basal split of an Eastern and a Western lineage during the Miocene-Pliocene transition, while the divergence among the Western European moles should have occurred in association to the Pliocene-Pleistocene climatic oscillations.

Chromosomal rearrangements, phenotypic variation and modularity: a case study from a contact zone between house mouse Robertsonian races in Central Italy.

Abstract The Western European house mouse, Mus musculus domesticus, is well‐known for the high frequency of Robertsonian fusions that have rapidly produced more than 50 karyotipic races, making it an ideal model for studying the mechanisms of chromosomal speciation. The mouse mandible is one of the traits studied most intensively to investigate the effect of Robertsonian fusions on phenotypic variation within and between populations. This complex bone structure has also been widely used to study the level of integration between different morphogenetic units. Here, with the aim of testing the effect of different karyotypic assets on the morphology of the mouse mandible and on its level of modularity, we performed morphometric analyses of mice from a contact area between two highly metacentric races in Central Italy. We found no difference in size, while the mandible shape was found to be different between the two Robertsonian races, even after accounting for the genetic relationships among individuals and geographic proximity. Our results support the existence of two modules that indicate a certain degree of evolutionary independence, but no difference in the strength of modularity between chromosomal races. Moreover, the ascending ramus showed more pronounced interpopulation/race phenotypic differences than the alveolar region, an effect that could be associated to their different polygenic architecture. This study suggests that chromosomal rearrangements play a role in the house mouse phenotypic divergence, and that the two modules of the mouse mandible are differentially affected by environmental factors and genetic makeup.

Mitochondrial phylogeography of the black rat supports a single invasion of the western Mediterranean basin

Abstract The black rat Rattus rattus is recognized as one of the world’s most harmful invasive species. It has spread across the globe by passive human transport and the dynamics of colonization have been investigated in several areas of the world. However, data for the Mediterranean basin are still lacking. We investigated the black rat colonization of the western Mediterranean basin by means of mitochondrial genes. Mitochondrial control region and cytochrome b gene were sequenced in order to quantify genetic diversity of western Mediterranean black rats. Maximum likelihood phylogenetic analysis based on cytochrome b was used to assign specimens to a specific lineage of the R. rattus species complex. The mitochondrial control region was used to reconstruct phylogeographic pattern by statistical parsimony network and to asses historical demography of western Mediterranean black rats. The results show an unexpectedly low diversity considering that the Mediterranean basin has been a trade route since very ancient times. The results mtDNA analysis are compatible with a single event of invasions of western Mediterranean by R. rattus.

The relevance of Italian museum collections for research and conservation: the case of mammals

The twentieth century saw the decline of interest toward museum collections and an increased support to ‘experimental’ and ‘evolutionary’ biology, implicitly recognising the opposite nature of the ‘old’ museum-based taxonomy. With few exceptions, such as those of Florence and Verona, Italian museums after World War II were pushed at the border of scientific activity by the academic world and had to fight for their survival. Examples from the USA and elsewhere show the increased relevance of modern mammal collections to several fields of research. Despite an increased and welcomed attention to the value of historical collections, there is still scarce awareness of the need and relevance of maintaining and implementing mammal collections in museums as a valuable, long-term, source of data in the field of conservation biology, faunistic, taxonomy, molecular biology and health monitoring. In the present paper we suggest to create a network between mammalogists and a number of mammal collections, with one museum serving as focal point for a national mammal collection.