Islands have long been recognized as distinctive evolutionary arenas leading to morphologically divergent species, such as dwarfs and giants. We assessed how body size evolution in island mammals may ...have exacerbated their vulnerability, as well as how human arrival has contributed to their past and ongoing extinctions, by integrating data on 1231 extant and 350 extinct species from islands and paleo islands worldwide spanning the past 23 million years. We found that the likelihood of extinction and of endangerment are highest in the most extreme island dwarfs and giants. Extinction risk of insular mammals was compounded by the arrival of modern humans, which accelerated extinction rates more than 10-fold, resulting in an almost complete demise of these iconic marvels of island evolution.
Extinctions have altered island ecosystems throughout the late Quaternary. Here, we review the main historic drivers of extinctions on islands, patterns in extinction chronologies between islands, ...and the potential for restoring ecosystems through reintroducing extirpated species. While some extinctions have been caused by climatic and environmental change, most have been caused by anthropogenic impacts. We propose a general model to describe patterns in these anthropogenic island extinctions. Hunting, habitat loss and the introduction of invasive predators accompanied prehistoric settlement and caused declines of endemic island species. Later settlement by European colonists brought further land development, a different suite of predators and new drivers, leading to more extinctions. Extinctions alter ecological networks, causing ripple effects for islands through the loss of ecosystem processes, functions and interactions between species. Reintroduction of extirpated species can help restore ecosystem function and processes, and can be guided by palaeoecology. However, reintroduction projects must also consider the cultural, social and economic needs of humans now inhabiting the islands and ensure resilience against future environmental and climate change.
The chronology of the extinction of the Balearic fossil bovid Myotragus balearicus in Mallorca and Menorca has been under discussion since its discovery in 1909, and especially in the last decades, ...thanks to the radiocarbon dates that have been obtained from several deposits of the island of Mallorca. Here, we present new radiocarbon dates of M. balearicus bones (including the most recent date ever obtained for the species, 4035 ± 32 BP, 2830–2470 cal. BC) that together with a newly published radiocarbon date for the evidence of the first human presence in the island (introduced Caprinae bone, 3884 ± 36 BP; 2470–2210 cal. BC) allow us to reduce the uncertainty period for the Myotragus extinction (UPME) in Mallorca from 1660 to 620 years (p > 95%) or even to 350 years (p > 90%) and to reject the hypotheses suggesting a climate change–driven (i.e. non-human) extinction of the species. This new scenario points to the causal relationship between the first human arrival and the M. balearicus extinction. The chronological gap between the earliest documented M. balearicus and the first documented human presence represents one of the shortest time periods documented between endemic megafauna and humans on any Mediterranean island.
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.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Stomatal density of plants may vary depending on environmental factors, such as CO2 concentration. Under the current atmospheric conditions, it is expected that leaves have different stomatal density ...than they had hundreds or thousands of years ago, due to the rise in CO2 in the atmosphere. Coprolites of the extinct Myotragus balearicus from Cova Estreta (Pollença, Mallorca), with a radiocarbon age of 3775–3640 cal. bc, have been used to study the diet of this bovid. A significant amount of epidermal fragments of Buxus was found in the faecal material. Three coprolites were used to estimate the stomatal density and stomatal index of Buxus epidermal fragments from this period. Samples of the endangered Buxus balearica, the sole species of Buxus currently present on Mallorca, and samples of the Buxus sempervirens, present in the nearest mainland, were also collected in different locations. Leaves were examined using microscopy to determine and compare the stomatal density and stomatal index between current plant material and coprolite material. The results indicated a higher value for stomatal index (12.71) and stomatal density (297.61 stomata/mm2) in leaves from the coprolites versus leaves of the living B. balearica and B. sempervirens species (7.99 and 227.77 stomata/mm2 respectively). These results could provide a palaeobotanic evidence of a change in atmospheric CO2 concentration since mid-Holocene in the Mediterranean basin.
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•A near complete mitogenome of the extinct shrew Nesiotites hidalgo is presented.•Molecular phylogeny of N. hidalgo agrees with its placement within Nectogalini.•Combined phylogeny ...confirms the relationship Nesiotites-Asoriculus with Soriculus.•Divergence estimates supports the faunal arrival to the Balearic Islands during MSC.•Retrieval of mitogenomes of fossils from marginal environments for DNA preservation.
The red-toothed shrews (Soricinae) are the most widespread subfamily of shrews, distributed from northern South America to North America and Eurasia. Within this subfamily, the tribe Nectogalini includes the fossil species Nesiotites hidalgo recorded from the Late Pleistocene to Holocene of the Balearic Islands (Western Mediterranean). Although there is a consensus about the close relationship between the extinct red-toothed shrew genera Nesiotites and Asoriculus based on morphology, molecular data are necessary to further evaluate the phylogenetic relationships of the Balearic fossils. We obtained a near complete mitochondrial genome of N. hidalgo, allowing the first molecular phylogenetic analysis of this species. Analyses based on 15,167 bp of the mitochondrial genome placed N. hidalgo as close relative to the extant Himalayan shrew (Soriculus nigrescens), and a combined analysis using molecular and morphological data confirm that N. hidalgo and Asoriculus gibberodon are sister-taxa with S. nigrescens as the immediate outgroup. Molecular clock and divergence estimates suggest that the split between N. hidalgo and its closest living relative occurred around 6.44 Ma, which is in agreement with the previously proposed colonisation of the Balearic Islands from mainland Europe by nectogaline shrews during the Messinian Salinity Crisis (5.97–5.33 My ago). Our results highlight that it is possible to retrieve genetic data from extinct small mammals from marginal environments for DNA preservation. Additional finds from the fossil record of Soricinae from the Eurasian Late Miocene/Early Pliocene are needed to shed further light on the still confusing taxonomy and paleobiogeography of this clade.
Abstract
The original bird fauna of most oceanic islands has been affected by recent extinction processes associated with human arrival and its subsequent impacts. In the volcanic Macaronesian ...archipelagos (Azores, Madeira, Selvagens, Canary Islands and Cape Verde), in the North Atlantic, the Late Quaternary fossil record indicates that there was formerly a higher avian diversity, including a high number of now extinct endemic species. This assemblage of extinct birds includes endemic insular quails (Galliformes: Phasianidae). In this study, we describe three newly discovered extinct species of quails, two of which inhabited the archipelago of Madeira (Coturnix lignorum sp. nov. from Madeira Island and Coturnix alabrevis sp. nov. from Porto Santo Island) and one from Cape Verde (Coturnix centensis sp. nov.). The fossil record also indicates the presence of additional species of extinct endemic quails on other Macaronesian islands. These birds plus the extinct Canary Island quail (Coturnix gomerae) indicate a high former endemic diversity of this genus in Macaronesia, a feature unique among oceanic archipelagos. Anatomical traits show that the new taxa were flightless ground dwellers, making them vulnerable to human interference, with their extinction being linked to human arrival and subsequent habitat alterations and the introduction of invasive species.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The Cova des Pas de Vallgornera is the longest cave of Mallorca (Balearic Islands, Western Mediterranean) and one of the 30 longest caves in the world. The exploration of one of the galleries allowed ...the discovery of a fossiliferous deposit of vertebrate remains in a remarkable preservation state. The fossil faunal complex found in this gallery is composed of up to 5 mammalian species (Myotragus aff. kopperi, Hypnomys onicensis, Nesiotites aff. ponsi, Rhinolophus aff. mehelyi and Pipistrellus sp.), at least 14 bird species (among them two Mallorcan endemic taxa: Pica mourerae and Athene vallgornerensis), one reptile (Podarcis aff. lilfordi) and one amphibian (Discoglossus sp.). This faunal composition is similar to the one recorded in the Pedrera de s'Ònix, a well known deposit from the Early Pleistocene of Mallorca, and shared morphological characteristics between taxa of both deposits suggest that the chronology of the Cova des Pas de Vallgornera should be considered Early Pleistocene as well. Both taxonomical analysis and chronology of this fauna furnished information on some speleological aspects of the cave.
Abstract We report a specimen of an insular black rat ( Rattus rattus ) from Illa den Colom (Menorca, Western Mediterranean) displaying a singular dental characteristic. It has no molar teeth but ...displays regular incisors. Its mere occurrence as a regular adult rat is puzzling and we attempted to evaluate what diet and morphological changes in jaw shape were promoted by the total lack of molars, and allowed the successful survival of this specimen. Two approaches were performed: first, bone tissue was analysed to obtain δ15 N and δ13 C values in order to estimate dietary preferences of the rat. Second, the shape of the jaw was analysed through elliptic Fourier analysis, using outlines as markers of diet. The values for C and N fractionation (−19.89‰ and 10.06‰, respectively) suggest that the molarless rat included animal food in the diet and not exclusively plant material as observed in other mainland rat populations. The morphometric analysis in which the shape of the molarless mandible falls into the range of omnivorous groups leads to a similar conclusion. The adult age of the specimen suggests that it fed efficiently enough with its incisors to allow a normal growth. Although displaying a lack of molar teeth, no deep changes in remodelling jaw morphology can be observed and its shape falls into the variation of regular murines. The molarless rat exemplifies that special ecological features on small islands allow the survival of aberrant morphotypes.
Stomatal density of plants may vary depending on environmental factors, such as CO
2
concentration. Under the current atmospheric conditions, it is expected that leaves have different stomatal ...density than they had hundreds or thousands of years ago, due to the rise in CO
2
in the atmosphere. Coprolites of the extinct Myotragus balearicus from Cova Estreta (Pollença, Mallorca), with a radiocarbon age of 3775–3640 cal. bc, have been used to study the diet of this bovid. A significant amount of epidermal fragments of Buxus was found in the faecal material. Three coprolites were used to estimate the stomatal density and stomatal index of Buxus epidermal fragments from this period. Samples of the endangered Buxus balearica, the sole species of Buxus currently present on Mallorca, and samples of the Buxus sempervirens, present in the nearest mainland, were also collected in different locations. Leaves were examined using microscopy to determine and compare the stomatal density and stomatal index between current plant material and coprolite material. The results indicated a higher value for stomatal index (12.71) and stomatal density (297.61 stomata/mm
2
) in leaves from the coprolites versus leaves of the living B. balearica and B. sempervirens species (7.99 and 227.77 stomata/mm
2
respectively). These results could provide a palaeobotanic evidence of a change in atmospheric CO
2
concentration since mid-Holocene in the Mediterranean basin.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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