Biology subjects

Heimburger, B.

Publications and source records attributed to Heimburger, B..

3 recordsLinked to original sources

bioRxiv2022

Population structure and genetic variance among local populations of an non-native earthworm species in Minnesota, USA

A variety of human activities have been identified as driving factors for the release and spread of invasive earthworm species in North America. Population genetic markers can help to identify locally relevant anthropogenic vectors and provide insights into the processes of population dispersal and establishment. We sampled the invasive European earthworm species Lumbricus terrestris at nine sites and several bait shops within the metropolitan area of Minneapolis-St. Paul in Minnesota, USA. We used microsatellite markers to infer genetic diversity and population structure, and 16S rDNA to address multiple introduction events, including bait dumping, which is a common source of L. terrestris introductions into the wild. Our results indicate multiple introductions but not from current bait dumping. Overall, genetic structure was low and earthworms >5000 m apart were genetically differentiated, except for one sampling location, indicating jump-dispersal followed by population establishment. Further, earthworms at one location north of Minneapolis established from one or few founder individuals, suggesting that earthworm invasions are ongoing. We therefore encourage further monitoring of earthworm populations using molecular markers, in order to disentangle the different human-related vectors contributing to the spread of earthworms and their establishment, which is essential to develop adequate management strategies.

molecular biology↗

bioRxiv2021

Rapid diversification of the Australian Amitermes group during late Cenozoic climate change

Late Cenozoic climate change led to the progressive aridification of Australia over the past 15 million years. This gradual biome turnover fundamentally changed Australias ecosystems, opening new niches and prompting diversification of plants and animals. One example is the Australian Amitermes Group (AAG), consisting of the Australian Amitermes and affiliated genera. Although it represents the most speciose and diverse higher termite group in Australia, little is known about its evolutionary history. We used ancestral range reconstruction and diversification analyses to illuminate 1) the origin and phylogenetic relationships of the AAG, 2) biogeographical processes leading to the current continent-wide distribution, and 3) timing and pattern of diversification in the context of late Cenozoic climate change. By estimating the first time-calibrated phylogeny, we show that the AAG is a monophyletic group, whose ancestor arrived ~11-10 million years ago from Southeast Asia. Ancestral range reconstruction indicates that Australias monsoon region was the launching point for a continental radiation that has been shaped by range expansions and within-area speciation rather than vicariance. We found that multiple arid species diversified from mesic and tropical ancestors in the Plio-Pleistocene, but also observed diversification in the opposite direction. Finally, we show that two pulses of rapid diversification coincided with past climate change during the late Miocene and early Pliocene. Consistent with rapid diversification, species accumulation slowed, likely caused by progressive niche saturation. This study provides a stepping stone for predicting the future response of Australias termite fauna in the face of human-mediated climate change.

evolutionary biology↗

bioRxiv2020

Haplotype divergence supports ancient asexuality in the oribatid mite Oppiella nova

Sex strongly impacts genome evolution via recombination and segregation. In the absence of these processes, haplotypes within lineages of diploid organisms are predicted to accumulate mutations independently of each other and diverge over time. This so-called Meselson effect is regarded as a strong indicator of the long-term evolution under obligate asexuality. Here, we present genomic and transcriptomic data of three populations of the asexual oribatid mite species Oppiella nova and its sexual relative Oppiella subpectinata. We document strikingly different patterns of haplotype divergence between the two species, strongly supporting Meselson effect like evolution and ancient asexuality in O. nova: (I) Variation within individuals exceeds variation between populations in O. nova but vice versa in O. subpectinata. (II) Two O. nova sub-lineages feature a high proportion of heterozygous genotypes and lineage-specific haplotypes, indicating that haplotypes diverged independently within the two lineages after their split. (III) The deepest split in gene trees generally separates haplotypes in O. nova, but populations in O. subpectinata. (IV) Tree topologies of the two haplotypes match each other. Our findings provide positive evidence for the absence of sex over evolutionary time in O. nova and suggest that asexual oribatid mites can escape the dead-end fate usually associated with asexual lineages.

evolutionary biology↗