Josep Antoni Alcover

Molecular dating of caprines using ancient DNA sequences of Myotragus balearicus, an extinct endemic Balearic mammal

BackgroundMyotragus balearicus was an endemic bovid from the Balearic Islands (Western Mediterranean) that became extinct around 6,000-4,000 years ago. The Myotragus evolutionary lineage became isolated in the islands most probably at the end of the Messinian crisis, when the desiccation of the Mediterranean ended, in a geological date established at 5.35 Mya. Thus, the sequences of Myotragus could be very valuable for calibrating the mammalian mitochondrial DNA clock and, in particular, the tree of the Caprinae subfamily, to which Myotragus belongs.ResultsWe have retrieved the complete mitochondrial cytochrome b gene (1,143 base pairs), plus fragments of the mitochondrial 12S gene and the nuclear 28S rDNA multi-copy gene from a well preserved Myotragus subfossil bone. The best resolved phylogenetic trees, obtained with the cytochrome b gene, placed Myotragus in a position basal to the Ovis group. Using the calibration provided by the isolation of Balearic Islands, we calculated that the initial radiation of caprines can be dated at 6.2 ± 0.4 Mya. In addition, alpine and southern chamois, considered until recently the same species, split around 1.6 ± 0.3 Mya, indicating that the two chamois species have been separated much longer than previously thought.ConclusionSince there are almost no extant endemic mammals in Mediterranean islands, the sequence of the extinct Balearic endemic Myotragus has been crucial for allowing us to use the Messinian crisis calibration point for dating the caprines phylogenetic tree.

A review on the effects of alien rodents in the Balearic (Western Mediterranean Sea) and Canary Islands (Eastern Atlantic Ocean)

Invasions of alien rodents have shown to have devastating effects on insular ecosystems. Here we review the ecological impacts of these species on the biodiversity of the Balearic and the Canary Islands. A total of seven species of introduced rodents (two rats, three mice, one dormouse, and one squirrel) have been recorded (six in the Balearics and four in the Canaries). Some of them can occasionally be important predators of nesting seabirds, contributing to the decline of endangered populations in both archipelagos. Rats are also known to prey upon terrestrial birds, such as the two endemic Canarian pigeons. Furthermore, rats actively consume both vegetative and reproductive tissues of a high number of plants, with potential relevant indirect effects on vegetation by increasing erosion and favoring the establishment of alien plants. In the Balearics, rats and mice are important seed predators of endemic species and of some plants with a restricted distribution. In the Canaries, rats intensively prey upon about half of the fleshy-fruited tree species of the laurel forest, including some endemics. In both archipelagos, alien rodents disrupt native plant–seed dispersal mutualisms, potentially reducing the chances of plant recruitment at the same time that they modify the structure of plant communities. We further suggest that alien rodents played (and play) a key role in the past and present transformation of Balearic and Canarian native ecosystems.

Extinctions and Local Disappearances of Vertebrates in the Western Mediterranean Islands

A landlocked sea between the Eurasian and African plates, the Mediterranean Sea may be thought of as an ocean in miniature (Margalef, 1985). Like other seas on the borderlands between contiguous plates (e.g., Antillean and Sundaland regions), the Mediterranean is rich in islands. The islands of the Mediterranean have a complex paleogeographical history. Some are properly described as “continental,” but others just as clearly resemble oceanic islands, and are named oceanic-like islands (Alcover et al., 1998). This is reflected in their biotic composition. On continental islands, species tend to be identical or nearly identical to those on the adjacent mainland, although much less diverse. In addition to their well-known tendency to exhibit great endemism at the species level, oceanic and oceanic-like islands also display very low diversity at higher taxonomic levels and disharmonious floral and faunal integration as compared with mainland areas of similar size (Alcover et al., 1998).

Paleogenomics in a Temperate Environment: Shotgun Sequencing from an Extinct Mediterranean Caprine

Background Numerous endemic mammals, including dwarf elephants, goats, hippos and deers, evolved in isolation in the Mediterranean islands during the Pliocene and Pleistocene. Most of them subsequently became extinct during the Holocene. Recently developed high-throughput sequencing technologies could provide a unique tool for retrieving genomic data from these extinct species, making it possible to study their evolutionary history and the genetic bases underlying their particular, sometimes unique, adaptations. Methodology/Principals Findings A DNA extraction of a ∼6,000 year-old bone sample from an extinct caprine (Myotragus balearicus) from the Balearic Islands in the Western Mediterranean, has been subjected to shotgun sequencing with the GS FLX 454 platform. Only 0.27% of the resulting sequences, identified from alignments with the cow genome and comprising 15,832 nucleotides, with an average length of 60 nucleotides, proved to be endogenous. Conclusions A phylogenetic tree generated with Myotragus sequences and those from other artiodactyls displays an identical topology to that generated from mitochondrial DNA data. Despite being in an unfavourable thermal environment, which explains the low yield of endogenous sequences, our study demonstrates that it is possible to obtain genomic data from extinct species from temperate regions.

Nesiotites rafelinensis sp. nov., the earliest shrew (Mammalia, Soricidae) from the Balearic Islands, Spain

This paper describes a new species of shrew from a fossiliferous bone breccia near to Calo den Rafelino (Mallorca, Spain). The site is stratigraphically and palaeontologically dated to the earliest Early Pliocene (MN13-14). Nesiotites rafelinensis sp. nov. (Mammalia, Soricidae) is arguably the earliest representative of the Nesiotites known to date, a clade restricted to the Balearic Islands. The new species combines primitive dental traits with a relatively large size. The primitive features relate N. rafelinensis more with Asoriculus gibberodon, the possible ancestor of Nesiotites, than any other representative of the genus. The large size interrupts a, otherwise, regular trend of increase of size from the comparatively small A. gibberodon to the recent very large N. hidalgo. The faunal assemblage of Calo den Rafelino represents the earliest evidence of the fauna that arrived to the Mallorca Island during the Messinian Salinity Crisis.

Molecular phylogeny and evolution of the extinct bovid Myotragus balearicus

Myotragus balearicus was a dwarf artiodactyl endemic to the Eastern Balearic Islands, where it evolved in isolation for more than 5 million years before becoming extinct between 3640 and 2135 cal BC (calibrated years BC). Numerous unusual apomorphies obscure the relationship between Myotragus and the extant Caprinae. Therefore, genetic data for this species would significantly contribute to the clarification of its taxonomic position. In this study, we amplify, sequence, and clone a 338-base pair (bp) segment of the mitochondrial cytochrome b (cyt b) gene from a >9Kyr Myotragus subfossil from la Cova des Gorgs (Mallorca). Our results confirm the phylogenetic affinity of Myotragus with the sheep (Ovis) and the takin (Budorcas). In each tree, the Myotragus branch is long in comparison with the other taxa, which may be evidence of a local change in the rate of evolution in cyt b. This rate change may be due to in part to an early age of first reproduction and short generation time in Myotragus, factors that are potentially related to the extreme reduction in size of the adult Myotragus as compared to the other Caprinae.

A new species of Myotragus Bate, 1909 (Artiodactyla, Caprinae) from the Early Pliocene of Mallorca (Balearic Islands, western Mediterranean)

Myotragus palomboi n.sp. (Artiodactyla, Caprinae) is described from the Early Pliocene of Mallorca (Balearic Islands, western Mediterranean). This species is the earliest representative of the Myotragus lineage known to date in the Balearic Islands. A metatarsal, and several teeth and postcranial remains were found in a karstic deposit located on the east coast of the island, near Calo den Rafelino (Manacor), together with remains of Hypolagus , two rodent species, an insectivore and several reptiles. The metatarsal and phalanges of the new bovid are short and robust and display a combination of characters only observed in Myotragus . The presence of a larger p2, a metatarsal robustness index lower than in M. pepgonellae (the earliest known species to date), together with the morphology of the incisors, all suggest that M. palomboi should be considered as the ancestor of M. pepgonellae . Short metapodials and the reduction of p2 displayed by M. palomboi could be linked to a first stage of evolution in insular conditions. The arrival of this bovid to the island of Mallorca probably took place during the Mediterranean Messinian Salinity Crisis (Late Miocene, 5.6–5.32 Ma ago). Although the relationship of the new taxon to other fossil caprines cannot be definitively established, it could be phylogenetically close to the Late Miocene European species Aragoral mudejar and Norbertia hellenica .

Mitochondrial DNA from Myotragus balearicus, an extinct bovid from the Balearic Islands>

DNA was extracted from teeth and bones of Myotragus balearicus, a bovid that evolved in isolation on the Balearic Islands (Western Mediterranean) from the end of the Miocene, becoming extinct 4,000 years BP, after the arrival of humans in the islands. The numerous morphological apomorphies of Myotragus, most strikingly its dwarfism, frontal eyes, and ever-growing incisors, obscure its phylogenetic relationships with extant bovids. Therefore, the recovery of genetic information from Myotragus is of significant interest to help clarify the taxonomic position of this species. In this study we amplified and sequenced a 95 bp (base pair) fragment of the mtDNA cytochrome b gene from 6,000-year-old specimens of Myotragus. Several experimental controls, such as amino acid analysis, independent reproduction in two different laboratories, and cloning of the PCR product, support the authenticity of the ancient DNA sequence recovered. Phylogenetic comparison with orthologous sequences from supposedly related extant genera (serow, goral, mountain goat, chamois, takin, sheep, goat, Himalayan tahr, arctic musk ox, barbary sheep, blue sheep, and saiga) from the Caprinae subfamily suggests that Myotragus is related to some of these species. However, the real phylogenetic position of Myotragus is difficult to assess, due to the lack of resolution of the present molecular study, which can be partially attributed to the short length of the genetic fragment recovered.

Mandible morphometrics, dental microwear pattern, and palaeobiology of the extinct Balearic Dormouse Hypnomys morpheus

Hypnomys morpheus is a giant endemic dormouse from the Pleistocene deposits of Mallorca and Menorca (Balearic Islands, Spain). The present paper aims to interpret the morphological divergence between the mandibles of Hypnomys and of its extant relative Eliomys, the outline of the mandible being used as a marker of the morphological divergence. By comparison with the mandible of Eliomys, the more massive mandible of Hypnomys has recorded an ecological shift of the insular lineage towards a more abrasive diet, including hard vegetable matter, and a different niche. A microwear analysis of the teeth of Hypnomys was simultaneously performed as it can shed light on the diet, and is independent from the comparison of the mandibles. Hypnomys possibly ate harder food items than Eliomys, and likely occupied most of the island environments. Hypnomys appears to have differentiated from its ancestral type toward a more generalized morphology because of the lack of competitors.

Body shape and life style of the extinct Balearic dormouse Hypnomys (Rodentia, Gliridae): new evidence from the study of associated skeletons.

Hypnomys is a genus of Gliridae (Rodentia) that occurred in the Balearic Islands until Late Holocene. Recent finding of a complete skeleton of the chronospecies H. morpheus (Late Pleistocene-Early Holocene) and two articulated skeletons of H. cf. onicensis (Late Pliocene) allowed the inference of body size and the calculation of several postcranial indexes. We also performed a Factorial Discriminant Analysis (FDA) in order to evaluate locomotory behaviour and body shape of the taxa. Using allometric models based on skull and tooth measurements, we calculated a body weight between 173 and 284 g for H. morpheus, and direct measurements of articulated skeletons yielded a Head and Body Length (HBL) of 179 mm and a Total Body Length of 295 mm for this species. In addition to the generally higher robustness of postcranial bones already recorded by previous authors, H. morpheus, similar to Canariomys tamarani, another extinct island species, displayed elongated zygopodium bones of the limbs and a wider distal humerus and femur than in an extant related taxon, Eliomys quercinus. Indexes indicated that Hypnomys was more terrestrial and had greater fossorial abilities than E. quercinus. This was also corroborated by a Discriminant Analysis, although no clear additional inference of locomotory abilities could be calculated.