Genomic consequences of colonisation, migration and genetic drift in barn owl insular populations of the eastern Mediterranean

The study of insular populations was key in the development of evolutionary theory. The successful colonisation of an island depends on the geographic context, and specific characteristics of the organism and the island, but also on stochastic processes. As a result, apparently identical islands may harbour populations with contrasting histories. Here, we use whole genome sequences of 65 barn owls to investigate the patterns of inbreeding and genetic diversity of insular populations in the eastern Mediterranean Sea. We focus on Crete and Cyprus, islands with similar size, climate and distance to mainland, that provide natural replicates for a comparative analysis of the impacts of microevolutionary processes on isolated populations. We show that barn owl populations from each island have a separate origin, Crete being genetically more similar to other Greek islands and mainland Greece, and Cyprus more similar to the Levant. Further, our data show that their respective demographic histories following colonisation were also distinct. On the one hand, Crete harbours a small population and maintains very low levels of gene flow with neighbouring populations. This has resulted in low genetic diversity, strong genetic drift, increased relatedness in the population and remote inbreeding. Cyprus, on the other hand, appears to maintain enough gene flow with the mainland to avoid such an outcome. Our work provides a comparative population genomic analysis of the effects of neutral processes on a classical island-mainland model system. It provides empirical evidence for the role of stochastic processes in determining the fate of diverging isolated populations.

Do Islanders Have a More Reactive Behavioral Immune System? Social Cognitions and Preferred Interpersonal Distances During the COVID-19 Pandemic

Insular populations have traditionally drawn a lot of attention from epidemiologists as they provide important insights regarding transmission of infectious diseases and propagation of epidemics. There are numerous historical instances where isolated populations showed high morbidity once a new virus entered the population. Building upon that and recent findings that the activation of the behavioral immune system (BIS) depends both upon one’s vulnerability and environmental context, we predicted that, during the COVID-19 pandemic, place of residence (island vs. mainland) explains a significant proportion of variance in preferred interpersonal distances, animosity toward strangers, and willingness to punish those who do not adhere to COVID-19 preventive measures. With 48 populated islands, Croatia provides a fruitful testing ground for this prediction. We also opted to explore relations among BIS-related variables (pathogen disgust, germ aversion, and perceived infectability) and social cognitions in a more natural context than has previously been done. The study was conducted online, on Croatian residents, during April and May 2020. As expected, the BIS variables contributed significantly to preferred interpersonal distances, negative emotions toward strangers, and willingness to punish those who do not adhere to COVID-19 preventive measures. Furthermore, our results showed that geographical location explained a significant amount of variance in preferred social (but not personal and intimate) distances and negative emotions toward foreigners. As Croatian islands are extremely frequent travel destinations, these differences between mainlanders and islanders cannot be explained by the lack of exposure to foreigners. Additionally, we found that scores on preferred interpersonal distances, pathogen disgust, and germ aversion were significantly higher compared to those obtained in Croatian samples before the COVID-19 pandemic. Furthermore, men scored higher in perceived infectability than before the COVID-19 pandemic, and women did not, which reflects the objectively higher risk of SARS-CoV-2 for men than for women. Taken together, our results support the notion that BIS is a highly adaptive and context-dependent response system, likely more reactive in more susceptible individuals.

A new species of leaf-toed gecko (Phyllodactylidae, Phyllodactylus) from María Cleofas Island, Nayarit, Mexico

We describe a new species of leaf-toed gecko of the genus Phyllodactylus from María Cleofas Island, the smallest island of Tres Marías Archipelago, Nayarit, México. Genomic, phylogenomic, and morphological evidence support that the new species presents a unique combination of diagnostic characters. Morphologically, the new species has a high number of tubercles, head to tail (mean 47), longitudinal ventral scales (mean 61), and third labial–snout scales (mean 26). Gene flow tests revealed the genetic isolation of insular populations from mainland counterparts. In addition, we confirmed the non-monophyly of P. homolepidurus and P. nolascoensis, and we show that the taxon P. t. saxatilis is a complex; therefore, we propose taxonomic changes within the saxatilis clade. The discovery of this new insular endemic species highlights the urgency of continued exploration of the biological diversity of island faunas of Mexico.

Ecology of the meadow spittlebug Philaenus spumarius in the Ajaccio region (Corsica) – I: spring

The meadow spittlebug, Philaenus spumarius (L.) (Hemiptera: Aphrophoridae), is the main vector in Europe of the recently detected plant pathogen bacterium Xylella fastidiosa Wells et al. (Xanthomonadales: Xanthomonadaceae). While the ecology of continental populations is well documented, nothing is known about the insular populations of P. spumarius, such as in Corsica, where the bacterium was detected in 2015. Hence, in an epidemiological context, the ecology of P. spumarius has been studied in a maquis landscape in the Ajaccio region between 2017 and 2019. Adults and nymphs were almost exclusively collected on Cistus monspeliensis L. (Cistaceae). However, very few specimens were collected in summer, suggesting a movement of the adults to sheltered habitats. Unfortunately, despite several trapping methods used, the location of adult summer habitat remains unknown for the studied population. It might be tempting to destroy the central plant host of P. spumarius populations. However, as spittlebug nymphs are highly polyphagous on low-growing plant species and as the females can lay eggs in any dead plant tissues, such practice could have limited the impact. Instead, the strong relationship between P. spumarius and C. monspeliensis could be used to monitor spittlebug populations, to limit/concentrate the means of insect control, or in an agronomic context to lure insects away from crops. Maintaining natural arboreal vegetation around agronomic systems could help decrease insect abundance – and potentially, pathogen load – on cultivated species. Such hypotheses need to be further studied by landscape experiments.

Molecular data suggest multiple origins and diversification times of freshwater gammarids on the Aegean archipelago

Our main aim was to investigate the diversity, origin and biogeographical affiliations of freshwater gammarids inhabiting the Aegean Islands by analysing their mtDNA and nDNA polymorphism, thereby providing the first insight into the phylogeography of the Aegean freshwater gammarid fauna. The study material was collected from Samothraki, Lesbos, Skyros, Evia, Andros, Tinos and Serifos islands as well as from mainland Greece. The DNA extracted was used for amplification of two mitochondrial (COI and 16S) and two nuclear markers (28S and EF1-alpha). The multimarker time-calibrated phylogeny supports multiple origins and different diversification times for the studied taxa. Three of the sampled insular populations most probably represent new, distinct species as supported by all the delimitation methods used in our study. Our results show that the evolution of freshwater taxa is associated with the geological history of the Aegean Basin. The biogeographic affiliations of the studied insular taxa indicate its continental origin, as well as the importance of the land fragmentation and the historical land connections of the islands. Based on the findings, we highlight the importance of studying insular freshwater biota to better understand diversification mechanisms in fresh waters as well as the origin of studied Aegean freshwater taxa.

A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae)

We review the species of Bidessus of Madagascar and describe Bidessus anjozorobe sp. nov. from material collected in Anjozorobe forest. Anjozorobe is part of the Anjozorobe-Angavo Protected Area, which is an important corridor of transition forest between typical eastern humid forests and the residual sub-humid forest of the Central Highlands. Bidessus longistriga Régimbart, 1895 and Bidessus perexiguus Kolbe, 1883 are widespread but endemic low-altitude species on Madagascar. Bidessus nesioticus Guignot, 1956 is an alpine species described from near the peak of the Ankaratra mountain massifs at 2500 m a.s.l. We recollected the species for the first time since its description, in Ankaratra and in a new area above 2000 m a.s.l. in the Andringitra mountain further south. Bidessus cf. nero Gschwendtner, 1933 is tentatively recorded for Madagascar for the first time but further studies are needed to test the status of mainland and insular populations. Bidessus apicidens Biström & Sanfilippo, 1986 has not been recollected on Madagascar since 1970. All species are endemic to Madagascar except potentially Bidessus cf. ceratus and Bidessus cf. nero described from Uganda and the Democratic Republic of the Congo, respectively. The older records of the two non-endemic species Bidessus complicatus Sharp, 1904 and Bidessus ovoideus Régimbart, 1895 on Madagascar could not be verified.