New biogeography papers

Two new papers from the lab have recently become available on-line.  The first is a global analysis of population structuring in Bactrocera dorsalis, a joint work between Zhi-hong Li’s Beijing lab and the QUT lab, first authored by Qin Yujia (Grace) and co-published with numerous other international colleagues.  The paper is remarkable for showing the extreme lack of structuring in this global pest.  The second paper is an entirely QUT one, investigating the population structuring of breadfruit fly, B. umbrosa, one of only six Dacini species which has a natural distribution which runs from Asia, across Wallacea, and into the western Pacific.  The work shows clear population structuring across Wallacea and proposes that the species was moved from the Pacific into Asia in pre-history.

Qin Y., Krosch M.N., Schutze M.K., Wang X., Prabhakar C.S., Susanto A., Hee A.K.W., Ekesi S., Badji K., Khan M., Huang Y., Wu J., Wang Q., Yan G., Zhu L., Zhao Z., Liu L., Clarke A.R., Li Z. 2018. Population structure of a global agricultural pest, Bactrocera dorsalis (Diptera: Tephritidae). Evolutionary Applications 11: 1990-2003.

Abstract:  Bactrocera dorsalis, the Oriental fruit fly, is one of the world’s most destructive agricultural insect pests and a major impediment to international fresh commodity trade. The genetic structuring of the species across its entire geographic range has never been undertaken, because under a former taxonomy B. dorsalis was divided into four distinct taxonomic entities, each with their own, largely non-overlapping, distributions. Based on the extensive sampling of six priori groups from 63 locations, genetic and geometric morphometric datasets were generated to detect macrogeographic population structure, and to determine prior and current invasion pathways of this species. Weak population structure and highly genetic diversity were detected among Asian populations. Invasive populations in Africa and Hawaii are inferred to be the result of separate, single invasions from South Asia; while South Asia is also the likely source of other Asian populations. The current northward invasion of B. dorsalis into central China is the result of multiple, repeated dispersal events, mist likely related to fruit trade. Results are discussed in the context of global quarantine, trade and management of this pest. The recent expansion of the fly into temperate China, with very few associated genetic changes, clearly demonstrates the threat posed by this pest to ecologically similar areas in Europe and North America.

Krosch M.N., Schutze M., Newman J., Strutt F., Bryant L.M., McMahon J., Clarke A.R. In the footsteps of Wallace: population structure in the Breadfruit fruit fly, Bactrocera umbrosa (F.) (Diptera: Tephritidae), suggests disjunction across the Indo-Australian Archipelago. Austral Entomology: in press.

Understanding the interplay between plant host and insect herbivore diversification underpins many areas of pure and applied research. The tephritid fruit fly Bactrocera umbrosa is a primary pest of a small number of Artocarpus species throughout Southeast Asia and the West Pacific. Recent molecular evidence supports a pattern of eastward migration and species diversification in Artocarpus. Here, we aimed to test whether population structure in B. umbrosa was associated with historical biogeographical barriers such as Wallace’s Line, and discuss observed patterns in the context of Artocarpus diversification. We used an integrative approach to explore population structure within B. umbrosa based on morphological (wing shape and aedeagus length) and molecular (mitochondrial COI and COII) data. Overall, aedeagi and wing centroid sizes were generally larger, and exhibited greater variation in the West Pacific than Southeast Asia. Molecular data agreed with this trend, and COI also showed a subtle but clear disjunction between regions associated with Weber/Lydekker’s Lines. Taken together, the West Pacific was supported as the putative origin of B. umbrosa, whereas movement westward into Southeast Asia occurred more recently, likely via a single colonisation event followed by highly restricted gene flow. Population structure in B. umbrosa does not reflect an ancient history of tracking Artocarpus diversification eastward out of Southeast Asia.