Tempo and mode of evolutionary radiation in Diabroticina beetles (genera Acalymma, Cerotoma, and Diabrotica)

Abstract

Adaptive radiation is an aspect of evolutionary biology encompassing microevolution and macroevolution, for explaining the principles of lineage divergence. There are intrinsic as well as extrinsic factors that can be postulated to explain that adaptive radiation has taken place in specific lineages. The Diabroticina beetles are a prominent example of differential diversity that could be examined in detail to explain the diverse paradigms of adaptive radiation. Macroevolutionary analyses must present the differential diversity patterns in a chronological framework. The current study reviews the processes that shaped the differential diversity of some Diabroticina lineages (i.e. genera Acalymma, Cerotoma, and Diabrotica). These diversity patterns and the putative processes that produced them are discussed within a statistically reliable estimate of time. This was achieved by performing phylogenetic and coalescent analyses for 44 species of chrysomelid beetles. The data set encompassed a total of 2,718 nucleotide positions from three mitochondrial and two nuclear loci. Pharmacophagy, host plant coevolution, competitive exclusion, and geomorphological complexity are discussed as putative factors that might have influenced the observed diversity patterns. The coalescent analysis concluded that the main radiation within Diabroticina beetles occurred between middle Oligocene and middle Miocene. Therefore, the radiation observed in these beetles is not recent (i.e. post-Panamanian uplift, 4 Mya). Only a few speciation events in the genus Diabrotica might be the result of the Pleistocene climatic oscillations.

Trophic interaction network and the evolutionary history of Diabroticina beetles (Chrysomelidae: Galerucinae)

“…Twenty‐four species were collected in the field in Mexico (Veracruz, Puebla, Oaxaca) and sequenced by us. The remaining 19 in‐group species and one out‐group species were included based on DNA sequences available in GenBank (Eben and Espinosa de los Monteros ). We used species from three of the four sections of Diabroticina: the Diabroticites, Cerotomites and Phyllecthrites.…”

“…Coalescent times for the splitting events within the Diabroticina beetles phylogeny were inferred with the aid of the computer software BEAST 1.8.0 (Drummond and Rambaut ). The tree recovered from previous phylogenetic analyses (Eben and Espinosa de los Monteros ) was used as a starting tree. A Yule process was set as prior for the tree model.…”

“…Diversification of the lineages Acalymma and Diabrotica started around 34 Ma. Among the lineages included in this study, Diabrotica speciated almost three times faster than Cerotoma, and Acalymma had an intermediate speciation rate (Eben and Espinosa de los Monteros ). These rates are reflected in the described species numbers for each of these three genera.…”

“…Metrics of network analysis, that is connectance, modularity, number of interactions and feeding specialization, were used. We chose 43 Diabroticina species with known host plant family or host species association for the adult beetles (Eben and Espinosa de los Monteros ). Data on host use were obtained from previous experiments and observations as well as from the literature (Branson and Krysan ; Krysan and Branson ; Krysan and Smith ; Eben ,b, ; Clark et al.…”

Back to the Origin: In Situ Studies Are Needed to Understand Selection during Crop Diversification

“…It is highly possible that associated microbes and insects have adapted to the milpa. Perhaps it should not be a surprise that the most devastating contemporary native insect pests of maize can all be collected from squash flowers (Metcalf and Lampman, 1989), and that several closely related species of leaf beetles in the genus Diabrotica damage maize, beans, and squash (Clark et al, 2001;Vidal et al, 2005;Eben and Espinosa de Los Monteros, 2013). There are many other unexplored questions on crops and biotic interactions in milpa systems such as: (1) To what extent have microbiomes, pathogens, mycorrhizae, herbivores, natural enemies, and pollinators adapted to polyculture and landrace traits?…”