Molecular systematics of Blepharida beetles (Chrysomelidae: Alticinae) and relatives

Habitat Specificity, Host Plants and Areas of Endemism for the Genera-Group Blepharida s.l. in the Afrotropical Region (Coleoptera, Chrysomelidae, Galerucinae, Alticini)

Simple Summary

Knowledge of the processes that generate biodiversity is a core-issue of any conservation strategy because it allows predicting the effects of environmental changes in the number and distribution of target taxa. Some phytophagous insects can be good potential indicators of such processes, thanks to their wide distribution and their sensitivity to climate change, due to the association with specific environments and host plants. Unfortunately, this ecological information is often lacking. However, statistical tools allow reconstructing the ecological features of interest, based on the presence–absence data of the taxa, the climatic and vegetational features of their distributional areas, and the available data about their host plants. In this paper, we apply some geostatistical methods to identify processes and patterns of biodiversity at a continental scale, focusing on a group of phytophagous insects widespread in sub-Saharan Africa.

Abstract

The genus Calotheca Heyden (Chrysomelidae) is mainly distributed in the eastern and southern parts of sub-Saharan Africa, with some extensions northward, while Blepharidina Bechyné occurs in the intertropical zone of Africa, with two subgenera, Blepharidina s. str. and Blepharidina(Afroblepharida) Biondi and D’Alessandro. These genera show different ecological preferences. Through an up-to-date presence–absence dataset, in the light of the terrestrial ecoregions of sub-Saharan Africa and the distribution of their possible host plants, we interpreted the pattern of occurrence of these three supraspecific taxa, by geostatistical analyses in GIS and R environments. The separation of Blepharidina from Calotheca was probably driven by changes in climate as adaptation to more xeric and warm environments with a major occupancy of semidesert and savannah habitats, especially in the Afroblepharida species. Based on our data and analyses, Calotheca is mainly associated with Searsia (Anacardiaceae), and Blepharidina is likely associated with Commiphora (Burseraceae). This hypothesis is also corroborated by the widespread and even dominance of the Commiphora plants in the ecoregions where both Blepharidina s.str. and, above all, Afroblepharida, are more common. The main areas of endemism of the two genera are also differently located: Calotheca in the temperate zone; Blepharidina within the intertropical belt.

Genomic Mining of Phylogenetically Informative Nuclear Markers in Bark and Ambrosia Beetles

Deep level insect relationships are generally difficult to resolve, especially within taxa of the most diverse and species rich holometabolous orders. In beetles, the major diversity occurs in the Phytophaga, including charismatic groups such as leaf beetles, longhorn beetles and weevils. Bark and ambrosia beetles are wood boring weevils that contribute 12 percent of the diversity encountered in Curculionidae, one of the largest families of beetles with more than 50000 described species. Phylogenetic resolution in groups of Cretaceous age has proven particularly difficult and requires large quantity of data. In this study, we investigated 100 nuclear genes in order to select a number of markers with low evolutionary rates and high phylogenetic signal. A PCR screening using degenerate primers was applied to 26 different weevil species. We obtained sequences from 57 of the 100 targeted genes. Sequences from each nuclear marker were aligned and examined for detecting multiple copies, pseudogenes and introns. Phylogenetic informativeness (PI) and the capacity for reconstruction of previously established phylogenetic relationships were used as proxies for selecting a subset of the 57 amplified genes. Finally, we selected 16 markers suitable for large-scale phylogenetics of Scolytinae and related weevil taxa.

Biology of Blepharida-group flea beetles with first notes on natural history of Podontia congregata Baly, 1865 an endemic flea beetle from southern India (Coleoptera, Chrysomelidae, Galerucinae, Alticini)

The biology, host plants, and pest status of Podontia Dalman, 1824 species are reviewed. Natural history of Podontia congregata Baly, 1865 a flea beetle endemic to southern India, is reported for the first time. It is distributed from the Western Ghats Mountains westward to the plains. Clusiaceae is reported as a new host plant family for Blepharida-group species, with Garcinia gummi-gutta (L.) N. Robson (Clusiaceae) as the host plant for Podontia congregata. Pentatomid bugs attack the larvae but not eggs, pupae, or adults. A new egg parasitoid species, Ooencyrtus keralensis Hayat and Prathapan, 2010 (Hymenoptera: Encyrtidae), was discovered. Aspects of Podontia congregata host selection, life cycle, and larval fecal defenses are consistent with its inclusion in the Blepharida-genus group.

Anti-predator defence drives parallel morphological evolution in flea beetles

Complex morphological or functional traits are frequently considered evolutionarily unique and hence useful for taxonomic classification. Flea beetles (Alticinae) are characterized by an extraordinary jumping apparatus in the usually greatly expanded femur of their hind legs that separates them from the related Galerucinae. Here, we examine the evolution of this trait using phylogenetic analysis and a time-calibrated tree from mitochondrial (rrnL and cox1) and nuclear (small subunits and large subunits) genes, as well as morphometrics of femora using elliptic Fourier analysis. The phylogeny strongly supports multiple independent origins of the metafemoral spring and therefore rejects the monophyly of Alticinae, as defined by this trait. Geometric outline analysis of femora shows the great plasticity of this structure and its correlation with the type and diversity of the metafemoral springs. The recognition of convergence in jumping apparatus now resolves the long-standing difficulties of Galerucinae-Alticinae classification, and cautions against the value of trait complexity as a measure of taxonomic significance. The lineage also shows accelerated species diversification rates relative to other leaf beetles, which may be promoted by the same ecological factors that also favour the repeated evolution of jumping as an anti-predation mechanism.

Macroevolutionary chemical escalation in an ancient plant-herbivore arms race

A central paradigm in the field of plant-herbivore interactions is that the diversity and complexity of secondary compounds in plants have intensified over evolutionary time, resulting in the great variety of secondary products that currently exists. Unfortunately, testing of this proposal has been very limited. We analyzed the volatile chemistry of 70 species of the tropical plant genus Bursera and used a molecular phylogeny to test whether the species' chemical diversity or complexity have escalated. The results confirm that as new species diverged over time they tended to be armed not only with more compounds/species, but also with compounds that could potentially be more difficult for herbivores to adapt to because they belong to an increasing variety of chemical pathways. Overall chemical diversity in the genus also increased, but not as fast as species diversity, possibly because of allopatric species gaining improved defense with compounds that are new locally, but already in existence elsewhere.

Comparative analysis of sequences and secondary structures of the rRNA internal transcribed spacer 2 (ITS2) in pollen beetles of the subfamily Meligethinae (Coleoptera, Nitidulidae): potential use of slippage-derived sequences in molecular systematics

A comparative analysis of ITS2 sequences and secondary structures in 89 species of pollen beetles of the subfamily Meligethinae (Coleoptera, Nitidulidae) was performed. The ITS2 folding pattern was highly conserved and comparable with the general model proposed for eukaryotes. Simple sequence repeats (SSRs) were responsible for most of the observed nucleotide variability (approximately 1-3%) and length variation (359-459bp). When plotted on secondary structures, SSRs mapped in expansion segments positioned at the apices of three ITS2 helices ('A', 'B' and 'D1') and appeared to have evolved under mechanisms of compensatory slippage. Homologies among SSRs nucleotides could not be unambiguously assigned, and thus were not useful to resolve phylogeny. However, slippage-derived motifs provided some preliminary genetic support for newly proposed taxonomic arrangements of several genera and subgenera of Meligethinae, corroborating existing morphological and ecological datasets.

The impact of herbivore-plant coevolution on plant community structure

Coevolutionary theory proposes that the diversity of chemical structures found in plants is, in large part, the result of selection by herbivores. Because herbivores often feed on chemically similar plants, they should impose selective pressures on plants to diverge chemically or bias community assembly toward chemical divergence. Using a coevolved interaction between a group of chrysomelid beetles and their host plants, I tested whether coexisting plants of the Mexican tropical dry forest tend to be chemically more dissimilar than random. Results show that some of the communities are chemically overdispersed and that overdispersion is related to the tightness of the interaction between plants and herbivores and the spatial scale at which communities are measured. As coevolutionary specialization increases and spatial scale decreases, communities tend to be more chemically dissimilar. At fairly local scales and where herbivores have tight, one-to-one interactions with plants, communities have a strong pattern of chemical disparity.