Biology subjects

Adams, M. W. D.

Publications and source records attributed to Adams, M. W. D..

5 recordsLinked to original sources

bioRxiv2025

Increases in invertebrate abundance and shifts in assemblage composition following Rodent Eradication on Lord Howe Island

Invasive species are one of the major threatening processes impacting biodiversity on islands. In particular, introduced rodents represent one of the most serious threats to island ecosystems, affecting a wide range of native plants, vertebrates and invertebrates. While nearly ubiquitous on human-modified islands, the last four decades have seen the advent of targeted rodent eradications, which have generally resulted in positive impacts for biodiversity. Invertebrates, which are crucial to the functioning of island ecosystems, are known to be negatively impacted by rodents, but their response to rodent removal is less well understood. The largest rodent eradication on an inhabited island was undertaken in 2019 on Australias Lord Howe Island, which successfully extirpated black rats (Rattus rattus) and house mice (Mus musculus) more than a century after their introduction. To examine the impacts of rodents on invertebrates on Lord Howe Island, we collected arboreal and terrestrial species both pre- and post-eradication and identified them to Order. Total invertebrate abundance increased after the eradication of rodents, alongside substantial shifts in assemblage composition, however Ordinal diversity did not change significantly. Orders with large increases in abundance included Isopoda and Blattodea, while the abundance of Coleoptera and Polydesmida did not change. In addition, the abundance of large invertebrates, which are presumably subject to stronger rat predation, rose dramatically following rodent eradication. Our results suggest an ecological rearrangement following the relaxation of predation pressure and augment documented evidence of improved biodiversity outcomes for forest tree species, seabirds and land birds.

ecology↗

bioRxiv2025

Island syndrome in the critically endangered Lord Howe Island cockroach Panesthia lata

Following island colonisation, organisms experience a unique array of selective pressures, giving rise to a somewhat predictable suite of morphological, demographic and ecological adaptations known as the "island syndrome". Studies of the island syndrome have provided valuable insights into processes of speciation, community assembly, adaptive radiation and ecological release, alongside many others. However, to date, behavioural aspects of island adaptation have comparatively received little scientific attention, especially among invertebrates. In this study we examined the agonistic, courtship and aggregation behaviour of the endangered Lord Howe Island cockroach Panesthia lata, and compared these to its Australian sister species Panesthia cribrata. Behavioural assays revealed that while courtship behaviour was relatively stable across the two species, there was a significantly lower incidence of male agonism in P. lata. In concordence, analyses of nuclear single-nucleotide polymorphisms showed that P. lata forms large aggregations of unrelated individuals, unlike most Panesthia species, which maintain stable family groups. These results align with previous findings of relaxed intraspecific aggression in island mammals and reptiles, providing novel evidence of behavioural island syndrome in an invertebrate. We also found that courtship behaviour did not vary when P. lata interacted with conspecifics from the same or different populations, suggesting that individuals from different populations will readily interbreed. This is a promising outcome for the conservation of this critically endangered species, which currently spans a fragmentary range consisting of small, insular populations.

evolutionary biology↗

bioRxiv2024

Pleistocene sea-level fluctuation shapes archipelago-wide population structure in the Endangered Lord Howe Island cockroach Panesthia lata

Studies of biogeographic processes have often centred islands as model systems, yet questions remain about the role of Pleistocene sea-level fluctuations in shaping islands biodiversity. One novel, potentially informative model system is the Lord Howe Island Group of Australia. Despite the World Heritage status of this archipelago, almost nothing is known of the biogeographic origins, evolutionary distinctiveness or genetic diversity of the ecological communities across its 28 islands. In this study, we focused on the cockroach Panesthia lata, an ecologically specialized invertebrate with one of the broadest recorded distributions of any LHIG species. To investigate the influence of Pleistocene sea-level fluctuations on LHIG fauna, we explored the phylogeography of P. lata using single-nucleotide polymorphisms and complete mitochondrial genomes. Our analyses reveal that the lineage on the permanently isolated islet Balls Pyramid is highly divergent from the remaining populations, while those on the episodically connected Lord Howe, Roach and Blackburn Islands experienced gene flow during the last glacial period. These results offer the first evidence that Pleistocene land bridges allowed for overland migration across the archipelago. Further, although P. lata was believed to have been locally extirpated by rodents on Lord Howe Island, we discovered two surviving, relict populations. We also detected high levels of inbreeding in all populations, emphasizing the need for ongoing conservation management. Finally, the combination of shallow genetic structure and low diversity suggests that genetic rescue from another island may be a viable strategy to conserve the Lord Howe Island population of P. lata, as well as other species that have been similarly impacted by rodents.

evolutionary biology↗

bioRxiv2024

Plio-Pleistocene decline of mesic forest underpins diversification in a clade of Australian Panesthia cockroaches

The progressive aridification of the Australian continent, and coincident decline of mesic forest, has been a powerful driver of allopatric and environmental speciation in native species. The relictual mesic forests of the eastern seaboard now harbor a diverse group of endemic fauna, including the wood-feeding cockroaches of the genus Panesthia, which reached the continent via two separate invasions from Melanesia. The more recent of these colonization events gave rise to a group of five recognized species, occurring in mainland woodlands, sclerophylls and rainforests, as well as the forests and grasslands of the Lord Howe Island Group. Due to limited sampling in molecular studies and doubt regarding the standing taxonomy, there is little certainty about relationships among the species and poor understanding of the effects of ancient climatic changes upon their evolution. We undertook a comprehensive phylogenetic analysis of the clade, using complete mitogenomes and nuclear ribosomal markers from nearly all known morphospecies and populations. Our time-calibrated phylogenetic analyses reveal six unrecognized, highly divergent lineages, and suggest that these have arisen primarily through vicariance as rainforests fragmented during Plio-Pleistocene glacial cycles (2-5 million years ago). Ancestral niche reconstructions also evidence a tropical rainforest origin for the group, followed by at least three niche transitions into drier forest, including one associated with the singular colonization of the Lord Howe Island Group. Finally, we find evidence of frequent, parallel wing reduction, in potential association with the contraction of forest habitats into small refugia. Our results reiterate the far-reaching role of ancient aridification in driving speciation, niche expansion and morphological evolution in Australian fauna.

evolutionary biology↗

bioRxiv2021

Changes in movement characteristics in response to private and social information acquisition of socially foraging fish

To overcome the cost of competition resulting from foraging in a group, individuals may balance their use of private (i.e., acquired from personal sampling) and social (i.e., acquired by watching other individuals) information to adjust their foraging strategy accordingly. Reliability of private information about environmental characteristics, such as the spatial distribution of prey, is thus likely to affect individual movement and social interactions during foraging. Our aim was to investigate how movement characteristics of foraging individuals changed as they acquired reliable private information about the spatial occurrence of prey in a foraging context. We allowed guppies (Poecilia reticulata) to develop the reliability of their private knowledge about prey spatial occurrence by repeatedly testing shoals in a foraging task under three experimental distributions of prey: 1) aggregated prey forming three patches located in fixed locations, 2) scattered distribution of prey with random locations, or 3) no prey (used as control). We then applied tracking methods to obtain individual time series of spatial coordinates from which we computed a suite of movement variables reflecting search effort, social proximity and locomotion characteristics during foraging, to examine changes occurring over repeated trials and to investigate which best explained foraging success. We show that foraging shoals became more efficient at finding and consuming food over the first three days by increasing their time spent active. Over time, individuals foraging on either scattered or aggregated prey travelled greater distances, showed an increasing distance to their closest neighbour and became slightly more stochastic in their acceleration profile, compared to control individuals. We found that behaviour changed as private information increased over time, with a clear behavioural shift occurring on the third testing day. Social proximity was the major predictor of foraging success in the absence of prior foraging information, while search effort became the most important predictors of foraging success as information increased. In conclusion, we show that individual movement patterns changed as they acquired private information. Contrary to our predictions, the spatial distribution of prey did not affect any of the movement variables of interest. Our results emphasise the importance of information in shaping movement behaviour in animals.

animal behavior and cognition↗