Biology subjects

Eyer, P. A.

Publications and source records attributed to Eyer, P. A..

7 recordsLinked to original sources

bioRxiv2023

Systematics of harvester ants (Messor) in Israel based on integrated morphological, genetic, and ecological data

Harvester ants of the genus Messor are considered ecosystem engineers, whose distribution is broadly influenced by a variety of environmental factors. Although distinct Messor species have been reported to inhabit different habitats, their taxonomy in Israel remains largely ambiguous, hampering the proper ecological characterization of these species. Here, we applied an integrative species delimitation approach combining morphology-based identification, phylogenetic analyses of nuclear and mitochondrial genes, and ecological niche modelling to investigate the phylogenetic relationships among Messor species in the small but ecologically diverse region of Israel. Our analyses of mitochondrial genes revealed the presence of at least 13 well-defined lineages, whereas only seven were supported by the analysis of the nuclear genes. However, the concatenated tree that included all the three markers supported 11 lineages. Among two of the lineages-in M. semirufus and in a group of ants closest in resemblance to M. grandinidus- we identified 3-4 clades that were well established on most trees, inviting further study. In addition, we reveal three undescribed species and raise two subspecies to species rank, highlighting the high diversity of harvester ants in Israel. Ecological niche modelling consistently supported the observed distribution of species, with soil type and average annual temperature being the most influential factors. These results demonstrate that species distribution modelling can serve as a valuable component of integrative species delimitation. We call for future studies to investigate these fascinating lineages of one of the most prominent and ecologically important genera of ants in the Mediterranean Basin.

ecology↗

bioRxiv2023

Immigration and seasonal bottlenecks: High inbreeding despite high genetic diversity in an oscillating population of the biting midge, Culicoides sonorensis (Diptera: Ceratopogonidae)

Most population genetic studies concern spatial genetic differentiation, but far fewer aim at analyzing the temporal genetic changes that occur within populations. Vector species, including mosquitoes and biting midges, are often characterized by oscillating adult population densities, which may affect their dispersal, selection, and genetic diversity over time. Here, we used a population of Culicoides sonorensis from a single site in California to investigate short-term (intra-annual) and long-term (inter-annual) temporal variation in genetic diversity over a three year period. This biting midge species is the primary vector of several viruses affecting both wildlife and livestock, thus a better understanding of the population dynamics of this species can help inform epidemiological studies. We found no significant genetic differentiation between months or years, and no correlation between adult populations and the inbreeding coefficient (FIS). However, we show that repeated periods of low adult abundance during cooler winter months resulted in recurring bottleneck events. Interestingly, we also found a high number of private and rare alleles, which suggests both a large, stable population, as well as a constant influx of migrants from nearby populations. Overall, we showed that the high number of migrants maintains a high level of genetic diversity by introducing new alleles, while this increased diversity is counterbalanced by recurrent bottleneck events potentially purging unfit alleles each year. These results highlight the temporal influences on population structure and genetic diversity in C. sonorensis and provide insight into factors effecting genetic variation that may occur in other vector species with fluctuating populations.

molecular biology↗

bioRxiv2022

Comparative genetic study of the colony structure and colony spatial distribution between the higher termite Amitermes parvulus and the lower, subterranean termite Reticulitermes flavipes in an urban environment

In insects, ecological competition has often resulted in phenotypic changes and modifications to foraging areas. In termites - and social insects as a whole - colonies cannot easily escape competition through the relocation of their colony. In these species, the outcomes of inter and intra-specific competition are influenced by different life history traits, such as colony size, breeding system (number and types of reproductives), food preference, tunneling patterns, nest site selection, and antagonism between colonies. Here, we investigated variation in breeding system and spatial distribution among colonies of a higher termite Amitermes parvulus and a subterranean termite Reticulitermes flavipes within an urban landscape. We first developed microsatellite markers as a tool to study these life history traits in A. parvulus. Second, we assessed competitive exclusion or tolerance of A. parvulus and R. flavipes colonies by determining their fine-scale distribution using monitoring stations on a grid site, and their large-scale distribution across an urban landscape. Third, we investigated the breeding system of A. parvulus colonies. We showed that the numerous colonies of R. flavipes inhabiting a restricted area contrast with the few, but spatially expansive colonies of A. parvulus, suggesting these species face different degrees of intra-specific competition. We showed that colonies of A. parvulus frequently merged together, and all of them were headed by inbred neotenic reproductives, two characteristics rarely observed in higher termites. Overall, our study revealed drastic differences in colony structure, breeding systems and foraging ranges between the two species. These differences may reflect differences in food preference and food availability between the two species allowing their co-existence within the same urban environment.

evolutionary biology↗

bioRxiv2022

Monopolization at the cost of desiccation: Reduced waterproofing cuticular hydrocarbons impairs nestmate discrimination in an ant

After humans, social insects represent one of the most complex groups of social organisms, relying on a well-organized communication system among colony members. The transfer of information among individuals is primarily based on cuticular hydrocarbons (CHC). These chemical compounds, produced by all insects, initially evolved to prevent water loss1. They were subsequently co-opted as semiochemicals to communicate various types of information. This includes nestmate recognition in social insects2,3, enabling different colonies to partition resources by ousting conspecific competitors. In this study, we report the near complete loss of CHC production by workers of the ant Nylanderia fulva. This absence of CHCs is a double-edged sword. It represents a causative agent in the ecological success of this ant species -- enabling the development of a large supercolony in its invasive range through limited ability to differentiate nestmates-- but increases the risk of suffering ecological stress through desiccation.

evolutionary biology↗

bioRxiv2022

Genetic diversity, paternal origin and pathogen resistance in Cataglyphis desert ants

Group diversity is usually associated with a reduced risk of disease outbreak and a slower rate of pathogen transmission. In social insects, multiple mating by queens (polyandry) evolved several times although reducing workers inclusive fitness. One major hypothesis suggests that polyandry has been selected for to mitigate the risk of outbreak thanks to increased genetic diversity within colonies. We investigated this hypothesis in the ant Cataglyphis mauritanica, in which nestmate workers are produced by several clonal, single-mated queens. Using natural colonies, we correlated genetic diversity with worker survival to a fungal entomopathogen. We further tested whether workers from different paternal lineages (but a common maternal genome) show differential resistance in experimentally singleor multiple-patriline groups, and whether an increased number of patrilines in a group improved disease incidence. We show that workers from distinct patrilines vary in their resistance to pathogen in single-patriline colonies, but the difference among patrilines disappears when they are mixed in multiple-patriline colonies. Furthermore, pathogen resistance was affected by the number of patrilines in a group, with twoand three-patriline groups being more resistant than single-patriline groups. However, resistance did not differ between groups made of two and three patrilines; similarly, it was not associated with genetic diversity in natural colonies. Overall, our results suggest that collective disease defenses might homogenize workers resistance from different patrilines and, thereby, stabilize colony resistance.

evolutionary biology↗

bioRxiv2021

Consistent signatures of urban adaptation in a native, urban invader ant Tapinoma sessile

Biological invasions are becoming more prevalent due to the rise of global trade and expansion of urban areas. Ants are among the most prolific invaders, with many exhibiting a multi-queen colony structure, dispersal through budding and a lack of inter-nest aggression. Although these characteristics are generally associated with the invasions of exotic ants, they may also facilitate the spread of native ants into novel habitats (e.g., urban areas). Native to North American forests, the odorous house ant Tapinoma sessile has become abundant in urban environments throughout the United States. Forest-dwelling colonies typically have a small workforce, inhabit a single nest, and are headed by a single queen, whereas urban colonies tend to be several orders of magnitude larger, inhabit multiple nests and are headed by multiple queens. Here, we explore and compare the population genetic and breeding structure of T. sessile within and between urban and natural environments in several localities across its distribution range. We found the social structure of a colony to be a plastic trait in both habitats, although extreme polygyny (i.e., nests with multiple queens) was confined to urban habitats. Additionally, polydomous colonies (i.e., nests lacking genetic differentiation and behavioral antagonism) were only present in urban habitats, suggesting T. sessile can only achieve unicoloniality within urbanized areas. Finally, we identified strong differentiation between urban and natural populations in each locality and continent-wide, indicating cities may restrict gene flow and exert intense selection pressure. Overall, our study highlights urbanizations influence in charting the evolutionary course for species.

evolutionary biology↗

bioRxiv2020

One tree, many colonies: colony structure, breeding system and colonization events of host trees in tunneling Melissotarsus ants

Ants exhibit a striking variety of lifestyles, including highly specialist or mutualist species. The minute blind workers of the African genus Melissotarsus chew tunnels in live trees to accommodate their obligate partner scale insects. Their modified legs are adapted for tunneling, but are unsuited for walking outside, confining these ants to their initial host tree. Here, we investigated whether this unique lifestyle results in complex patterns of genetic diversity at different scales, from the same tree to different populations. Using 19 microsatellite markers, we assessed their mating strategy and colony structure among and across populations in South Africa. We showed that only one queen reproduces within a colony, mated with up to three males. Yet, several inseminated dealate queens are present in colonies; one probably replaces the older queen as colonies age. The reproduction of a single queen per colony at a given time results in genetic differentiation between colonies, even those located on the same tree. Overall, we discussed how the slow process of colony digging under the bark and the lack of worker patrolling above the bark might result in reduced competition between colonies and allow several secluded colonies to cohabit in a cramped space on a tree.

evolutionary biology↗