The blowfly Chrysomya latifrons inhabits fragmented rainforests, but shows no population structure

Abstract

Climate change and deforestation are causing rainforests to become increasingly fragmented, placing them at heightened risk of biodiversity loss. Invertebrates constitute the greatest proportion of this biodiversity, yet we lack basic knowledge of their population structure and ecology. There is a compelling need to develop our understanding of the population dynamics of a wide range of rainforest invertebrates so that we can begin to understand how rainforest fragments are connected, and how they will cope with future habitat fragmentation and climate change. Blowflies are an ideal candidate for such research because they are widespread, abundant, and can be easily collected within rainforests. We genotyped 188 blowflies (Chrysomya latifrons) from 15 isolated rainforests and found high levels of gene flow, a lack of genetic structure between rainforests, and low genetic diversity – suggesting the presence of a single large genetically depauperate population. This highlights that: (1) the blowfly Ch. latifrons inhabits a ~ 1000 km stretch of Australian rainforests, where it plays an important role as a nutrient recycler; (2) strongly dispersing flies can migrate between and connect isolated rainforests, likely carrying pollen, parasites, phoronts, and pathogens along with them; and (3) widely dispersing and abundant insects can nevertheless be genetically depauperate. There is an urgent need to better understand the relationships between habitat fragmentation, genetic diversity, and adaptive potential–especially for poorly dispersing rainforest-restricted insects, as many of these may be particularly fragmented and at highest risk of local extinction.

Population structure and interspecific hybridisation of two invasive blowflies (Diptera: Calliphoridae) following replicated incursions into New Zealand

“…Thus, our findings suggest that the high dispersal capabilities of blowflies, and a general absence of dispersal barriers, have resulted in limited genetic differentiation over large geographical distances. Similar findings have been reported in Australian Chrysomya (Butterworth et al., 2023 ) and North American Phormia regina (Picard & Wells, 2009 )—though substantial genetic differentiation has been shown in other species (e.g. North American Lucilia sericata ; Picard & Wells, 2010 ).…”

“…Chrysomya (Butterworth et al, 2023) and North American Phormia Calliphora hilli (neutral data set: 16,636 SNPs; optimal K = 2) and (b) Calliphora stygia (neutral data set: 12,841 SNPs; optimal K = 2) produced using sparse non-negative matrix factorisation (sNMF). Admixture proportions showing K = 2-5 are presented, with populations in order from left to right corresponding to the top of the North Island, through to the bottom of the South Island of New Zealand, followed by Australia.…”

“…Yet we understand little about their population structure and the extent to which genetic processes, such as hybridisation and gene flow, operate during or after invasion. Such questions are particularly interesting for blowflies, given that they are highly vagile, excellent dispersers (Butterworth et al, 2023;Tsuda et al, 2009) that may be expected to maintain high rates of population connectivity post-invasion. Furthermore, research under laboratory conditions has demonstrated that C. stygia can produce hybrids with C. albifrontalis in Australia and C. hilli can produce hybrids with C. varifrons-suggesting that hybridisation within the species complex may be occurring in the wild (Monzu, 1977;Wallman & Adams, 1997), though this has not yet been confirmed using genomic data.…”

“…Such questions are particularly interesting for blowflies, given that they are highly vagile, excellent dispersers (Butterworth et al., 2023 ; Tsuda et al., 2009 ) that may be expected to maintain high rates of population connectivity post‐invasion. Furthermore, research under laboratory conditions has demonstrated that C .…”