Phylogenetic relationships in the Neotropical bruchid genus Acanthoscelides (Bruchinae, Bruchidae, Coleoptera)

Adaptation to host-plant defences through key innovations is a driving force of evolution in phytophagous insects. Species of the neotropical bruchid genus Acanthoscelides Schilsky are known to be associated with specific host plants. The speciation processes involved in such specialization pattern that have produced these specific associations may reflect radiations linked to particular kinds of host plants. By studying host-plant associations in closely related bruchid species, we have shown that adaptation to a particular host-plant (e.g. with a certain type of secondary compounds) could generally lead to a radiation of bruchid species at the level of terminal branches. However, in some cases of recent host shifts, there is no congruence between genetic proximity of bruchid species, and taxonomic similarity of host plants. At deeper branches in the phylogeny, vicariance or long-distance colonization events seem to be responsible for genetic divergence between well-marked clades rather than adaptation to host plants. Our study also suggests that the few species of Acanthoscelides described from the Old World, as well as Neotropical species feeding on Mimosoideae, are misclassified, and are more closely related to the sister genus Bruchidius .     

Mortality factors affecting the leaf-mining stages of Phyllonorycter (Lepidoptera: Gracillariidae) on oak and birch 2. Biology of the parasite species

Parasitic Hpenoptera attacking Phyllonorycter species mining leaves of oak and birch were studied at a Cheshire locality during 1974. The host developmental stages killed, and attacked, by each parasite species are analysed. Smaller species and males tend to kill earlier Phyllonorycter instars than do larger species and females, and certain of the endoparasites as well as the ectoparasites must discriminate between small hosts which receive haploid eggs and large hosts which receive diploid eggs. Host-feeding is very widely practised, and facultative hyperparasitism is engaged in by all except the braconids and a few specialized chalcids. The biology of a parasite species generally allows its allocation to one of three groups according to the size of host larva that it attacks, whether it is endoparasitic or ectoparasitic, whether or not the host continues to develop after parasitization, the extent of its hyperparasitic behaviour, its reproductive capacity, and the width of its host range. Different strategies, together with different specific host and habitat preferences, provide the basis for parasite complexes of high species diversity.     

Alternative seed defence mechanisms in a palo verde (Fabaceae) hybrid zone: effects on bruchid beetle abundance

Abstract.

• 1 We asked three questions about the patterns of relative abundance of insect herbivores across host plant taxa at a palo verde hybrid zone. (1) What is the morphological structure of the hybrid zone and does this suggest a certain pattern of introgression? (2) How are putative parental seed defence mechanisms expressed in hybrid plants? (3) Do ovipositing females prefer host plant taxa on which their offspring have best survivorship?
• 2 Morphologically, hybrids were either intermediate or tended to resemble one parental species. Previous studies have suggested that unidirectional introgression results in loss of parental defence mechanisms against herbivores. Hybrid plants in general lacked seed coat resistance and early pod abscission which are known to act as plant defence mechanisms against bruchid beetles in the parental palo verde trees.
• 3 All other sources of bruchid mortality that we examined did not vary across parental and hybrid taxa, with the possible exception of egg parasitism which occurred at a lower frequency on one parental palo verde species.
• 4 Thus, survivorship of bruchid offspring should be greater on hybrid palo verdes.
• 5 Patterns of egg densities suggested that females may prefer hybrid hosts in some years but not others. An oviposition choice experiment conducted in the field, however, showed bruchids have no preference for hybrids over one of the parental species.
• 6 These results suggest that some insect herbivores may have higher densities on hybrid host plants because they are less resistant.

     

Determinants of oviposition in Acanthoscelides obtectus: a nonconformist bruchid

Abstract. Acanthoscelides obtectus is atypical of bruchids found in stored seeds because females do not attach eggs individually to host seeds but scatter them irregularly among potential hosts. In other respects, its life history resembles that of other species and comparison provides evidence for the adaptive nature of their behaviour. Individual females differ dramatically in the temporal pattern of their oviposition. The hypothesis is proposed that this is an adaptation to life in heterogeneous habitats. Oviposition is not regulated by host availability to the same extent as in other bruchids, providing evidence that regulation of the number of eggs laid by species which stick eggs to host seeds is an adaptation to the abundance of hosts. The continued presence of males and opportunity for multiple matings does not affect fecundity or egg viability. Females preferentially lay on clean seeds when provided with a choice between them and seeds previously exposed to other adult beetles. However, they do not appear to be deterred by, or cannot detect, the presence of larvae infesting seeds. Other bruchid species avoid such seeds that they can identify by the occurrence of egg cases and pheromones. The number of eggs laid is influenced by the host cultivar available for oviposition. Oviposition by A. obtectus appears to be an adaptation to both storage environments and the heterogeneous environment of a growing crop or uncultivated land. Its behaviour suggests an ancestral condition in bruchids and the changes which might have occurred in the ecology of other bruchid species as they have adapted to become pests of human seed stores.     

Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforest

Abstract.  1. Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce.
2. Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea.
3. A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80–92 species.
4. Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts.
5. In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae).
6. Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families.     

Genetic differentiation associated with host plants and geography among six widespread species of South American Blepharoneura fruit flies (Tephritidae)

Tropical herbivorous insects are astonishingly diverse, and many are highly host‐specific. Much evidence suggests that herbivorous insect diversity is a function of host plant diversity; yet, the diversity of some lineages exceeds the diversity of plants. Although most species of herbivorous fruit flies in the Neotropical genus Blepharoneura are strongly host‐specific (they deposit their eggs in a single host plant species and flower sex), some species are collected from multiple hosts or flowers and these may represent examples of lineages that are diversifying via changes in host use. Here, we investigate patterns of diversification within six geographically widespread Blepharoneura species that have been collected and reared from at least two host plant species or host plant parts. We use microsatellites to (1) test for evidence of local genetic differentiation associated with different sympatric hosts (different plant species or flower sexes) and (2) examine geographic patterns of genetic differentiation across multiple South American collection sites. In four of the six fly species, we find evidence of local genetic differences between flies collected from different hosts. All six species show evidence of geographic structure, with consistent differences between flies collected in the Guiana Shield and flies collected in Amazonia. Continent‐wide analyses reveal – in all but one instance – that genetically differentiated flies collected in sympatry from different host species or different sex flowers are not one another's closest relatives, indicating that genetic differences often arise in allopatry before, or at least coincident with, the evolution of novel host use.     

A revision of the genus Mecistostethus Marseul (Histeridae, Histerinae, Exosternini)

We revise the genus Mecistostethus Marseul, sinking the monotypic genus Tarsilister Bruch as a junior synonym. Mecistostethus contains six valid species: Mecistostethus pilifer Marseul, Mecistostethus loretoensis (Bruch), comb. n., Mecistostethus seagorumsp. n., Mecistostethus carltonisp. n., Mecistostethus marseulisp. n., and Mecistostethus flechtmannisp. n. The few existing records show the genus to be widespread in tropical and subtropical South America, from northern Argentina to western Amazonian Ecuador and French Guiana. Only a single host record associates one species with the ant Pachycondyla striata Smith (Formicidae: Ponerinae), but it is possible that related ants host all the species.     

Optimal Xylocoris flavipes (Reuter) (Hemiptera: Anthocoridae) density and time of introduction for suppression of bruchid progeny in stored legumes

The influences of both predator density and elapsed time between initial infestation and introduction of predators were determined for suppression of bruchids infesting stored grain legumes by Xylocoris flavipes (Reuter) (Hemiptera: Anthocoridae). Predator density treatments consisted of zero, one, two, three, or five male:female pairs of adult X. flavipes added to experimental arenas 0, 24, or 120 h after bruchid introduction. Suppression of Acanthoscelides obtectus approached eradication with all predator treatments. For all other bruchid species evaluated (Callosobruchus analis, C. chinensis, C. maculatus, and Zabrotes subfasciatus), the most effective predator density and addition time (five predator pairs at 0 h) resulted in an approximately 50% reduction of emerging F1 bruchids compared with progeny produced in arenas without predators. The predator addition time of 0 h, when predators were added to experimental arenas simultaneously with the pest species, was determined to be the universally most efficacious treatment time. Predator density above one pair but lower than five pairs was less influential overall when X. flavipes was added 24 or 120 h after initial bruchid infestation; however, maximum suppression was achieved at approximately two predator pairs and not significantly improved on with increased predator density. Our results indicate that the most effective biological control of pest bruchids would occur when X. flavipes is added as soon as possible after legumes are stored.     

Molecular systematics and biogeography of the bent-wing bat complex Miniopterus schreibersii (Kuhl, 1817) (Chiroptera: Vespertilionidae)

The complete mitochondrial ND2 gene (1037 bp) was sequenced to examine relationships within the bent-wing bat complex, Miniopterus schreibersii (Family Vespertilionidae). It was found that M. schreibersii is a paraphyletic assemblage comprising several species. Two major lineages were identified, one of which was restricted to the Palearctic-Ethiopian regions and the other to the Oriental-Australasian regions. This pattern of differentiation was mirrored by the genus as a whole. Speciation and differentiation within the genus Miniopterus appears to have a hierarchical geographical pattern. The earliest divergence corresponds to the Ethiopian-Palearctic and the Oriental-Australasian biogeographical zones. This early divergence is then followed by radiations within each of the Ethiopian, Oriental and Australasian regions. The study also revealed that the number of species currently recognized (11 or 13) is a gross underestimate of the number of actual species. The emerging picture is one of a relatively speciose genus with most species having relatively restricted distributions; few, if any, occur in more than one biogeographical region.     

Host relations, life cycles and multiparasitism in some parasitoids of aphidophagous Syrphidae (Diptera)

Abstract. 1. Records of parasitism from the field and host choice experiments suggest that most parasitoids of syrphids are monophagous. A few are oligophagous.
2. To elicit egg release, females require a stimulus from the host haemolymph. Differential response to haemolymph cues by females may account for the observed pattern of host relations.
3. Differences in host ranges and timing of female flight periods probably characterize most of the parasitoids studied.
4. In one case of two monophagous parasitoids, Diplazon pectoratorius (Thunberg) and Syrphophilus tricinctorius (Thunberg) attacking the same host Syrphus ribesii (L.) no partitioning was found. Stricinctorius is, however, a superior intrinsic competitor.     

The Macroevolution of our Ancient Lineage: What We Know (or Think We Know) about Early Hominin Diversity

Quantitative, evolutionary models that incorporate within- and between-species variation are critical for interpreting the fossil record of human diversity, and for making taxonomic distinctions. However, small sample sizes, sexual dimorphism, temporal trends, geographic variation, and the limited number of relevant extant models have always made the consideration of variation difficult for paleoanthropologists. Here we provide a brief overview of current early hominin diversity. We then argue that for many species our limited understanding of within species variation hampers our ability to make taxonomic decisions with any level of statistical certainty. Perhaps more significantly, the underlying causes of between-species variation among early hominins are poorly studied. There have been few attempts to correlate aspects of the phenotype with meaningful evidence for niche differentiation, to demonstrate the selective advantage of traits, or to provide other evidence for macroevolutionary divergence. Moreover, current depictions of vast pattern (but not size) diversity are inconsistent with expectations derived from most other extant primate clades that have adaptively radiated. If indeed the early hominin record is highly speciose, the reasons for this remain unclear.     

Evolutionary aspects of host plant specialisation – a study on bruchids (Coleoptera: Bruchidae)

We have studied the relationship of bruchids and their legume hosts by extensive field sampling throughout Hungary over 17 years and by rearing the beetles from the samples in the laboratory. The value of the system lies in the accuracy of host affiliations. A total of 138 species and subspecies of plants were sampled, representing approximately 87% of the Leguminosae in Hungary. Only 51 legume species (37.0%) harboured bruchids (12 Bruchus spp. and 15 Bruchidius spp). Bruchids occurred in 38.3% of the host plant samples. Thirty-seven plant species congeneric with bruchid host species were unoccupied by bruchids.
The degree of host specificity ranged from monophagy (at least ecological monophagy) to oligophagy. On the basis of presence/absence data we tested the null hypothesis assuming that plant taxa and seed consuming bruchid species form congruent phyletic relations at the species level. We argue that the case for coevolution between the beetles and their hosts is weak. A comparison of the available taxonomic relationships (and presumed phylogenies) best fits a case of sequential evolution, with stronger phylogenetic conservatism in Bruchus species than in Bruchidius species. Bruchid and host plant taxa showed rough congruence only at the tribe level. We suggest that host shifts are best explained by the changes in the bruchids' chemosensory system that determines the females' host selection behaviour.     

Diversity and spacio‐temporal distribution of mushrooms in a Nigerian savanna: implication for their conservation

We surveyed the macrofungi of an area dominated by northern Guinea savanna habitats in north‐east Nigeria. A total of 93 different species of mushrooms were found in the study area. These species belong to 29 different families, most species belonging to the family Agaricaceae, Lyophyllaceae, Bolbitiaceae, Pluteaceae and Polyporaceae. A total of 48 species belonged to the Agaricaceae, followed by Lyophyllaceae represented by 6 species. The micro‐habitats of mushrooms in the study area include wood, soil around dead tree stump, waste dump, cow dung, fallow, arable land, and 22 different living trees species. The most important habitats in term of mushroom species diversity were Parkia biglobosa, Tamarindus indica and dead wood. The Parkia biglobosa tree had the highest species richness (45) and species diversity (Shannon diversity index, SDI: 3.6). Tamarindus indica was the second, having 28 species richness and 2.7 SDI. These were followed by dead wood where 22 different mushroom species were recorded and has of 2.1 SDI. Also, these three habitats (Parkia biglobosa, dead wood and Tamarindus indica) had the highest number of mushroom species (14, 8 and 6 respectively) that were confined to them. Most of the other mushroom species were confined to only one microhabitat. There was no statistically significant difference in mushroom abundance between arable land and fallow. Collectively, the indigenous trees were associated by more mushroom species (63) than the exotic trees (20) and the indigenous trees also had significantly higher mushroom abundance than the exotic trees. However, the non‐indegenous trees had more species forming mycorrhiza than the indegenous trees, presumaby because the former were able to form symbioses with both native fungi and introduced species from their origina habitats. Inter‐annual variation of mushroom species diversity was also observed. Human activities contribute positively to mushroom diversity in the study area by creating some unique micro‐habitats that support the growth of certain unique mushroom species. Therefore, for maximum conservation of mushroom diversity, conservation measures excuding all human activities should be avoided.     

Hummingbird diversity, food niche characters, and assemblage composition along a latitudinal precipitation gradient in the Bolivian lowlands

As for many other taxa, hummingbird diversity declines away from the equator, but the causes for this decline are still disputed and might involve, among others, climatic factors or the availability of food resources. Because hummingbirds are one of the classical examples for plant–animal coevolution, it has been proposed that the diversity of hummingbird assemblages might depend on the diversity of food plants available. We tested this hypothesis by studying the hummingbird assemblages and their food plants for 1 year at six sites along a 660-km-long transect in Bolivian lowland forests extending from the southernmost Amazonian rain forests to dry Chaco forests. Hummingbird diversity was higher in the northern three sites as compared to the southern ones, with an abrupt decline in species numbers and a corresponding change in taxonomic composition at the boundary from evergreen to drought deciduous forests. Hummingbird diversity and abundance were only weakly correlated to climatic factors or to the diversity of humming-visited flowers, but strongly to the seasonal abundance of flowers. The overlap in nectar diet between hummingbird species depended on the number of plant species: when numerous species were available, the hummingbirds segregated by feeding preferences, but when few flowers were available, all hummingbirds fed on the same plants. We conclude that the local diversity of hummingbird species is not primarily determined by the diversity of food plants, but rather by the abundance of flowers available at any given point in time.     

Aphid infestation promotes survival of a seed predator: observations and experiments on a tritrophic community module

We investigated whether aphid presence and abundance influence the survival of an endophagous pre-dispersal seed predator of the same host plant. We studied a terrestrial community module consisting of one plant (Laburnum anagyroides) and four insect species/groups (an aphid, Aphis cytisorum, a pre-dispersal seed predator bruchid, Bruchidius villosus, aphid-attending ant species, and parasitoids of the bruchid). Two complementary investigations were carried out in parallel: (a) a plant-aphid-ant complex was experimentally manipulated by excluding aphids, ants, or both for 5 years to assess their impacts on the seed predator’s survival and parasitism rate; and (b) different aphid infestation levels on randomly selected infructescences were correlated with plant traits, nutrient allocation pattern, and variables of seed predator’s survival, such as the number of eggs laid and adults emerged influenced by parasitoid activity, for 7 years. We found that ants did not affect bruchid oviposition negatively, but egg-parasitism was significantly decreased by their presence. Plant traits, such as the number of seeds and seed mass, as well as seed predator performance were negatively affected by heavy aphid infestation. Seed predator -infested seeds had no effect on the mass of remaining seeds in the pods. This study suggests that aphids were nevertheless promoting bruchid abundance and survival, depending on their infestation rate.     

Post-dispersal predation of Acacia farnesiana seeds by Stator vachelliae (Bruchidae) in Central America

Summary Post-dispersal seed predation by the bruchid beetle Stator vachelliae was investigated in Santa Rosa National Park, Costa Rica. This insect finds the seeds of the leguminous Acacia farnesiana in the feces of horses, deer, and ctenosaur lizards, the current major dispersers. Patterns of oviposition and pre-adult survival of beetles in the seeds were investigated in a series of experiments using fresh horse dung. S. vachelliae never minded into the dung balls, attacking only those seeds located on the surface. Fresh horse dung did not attract insects more readily than dry dung. The proportion of seeds attacked was not related to their density in a defecation, and was similar in three areas with different densities of the host plant. In a fourth area with no fruiting A. farnesiana shrubs all seeds survived insect predation. Bruchids attacked a greater proportion of seeds at 1 m than at 5 m from the edge of the shrub's crown. Seeds were mainly removed from horse dung by rodents with similar intensity in all areas and at both distances; this seed removal interfered with bruchid oviposition and probably with bruchid survival. S. vachelliae oviposited less frequently on seeds in dung fully exposed to sun. When oviposition on a dung pile was high, the distribution of eggs on the seeds was clumped, suggesting that some seeds were preferred to others. By the end of the dry season, bruchids stopped attacking the seeds. The results show that the fate of both seeds and bruchids is greatly influenced by the location and time of defecation.     

How host larval age, and nutrition and density of the parasitoid Dinarmus basalis (Hymenoptera: Pteromalidae) influence control of Acanthoscelides obtectus (Coleoptera: Bruchidae)

Choice of the targeted host developmental stage, regulation of parasitoid numbers released and introduction of food supplements are operational factors with a potential to influence the level of biological control. In a closed laboratory storage system maintained over two generations of the host, the impact of these three parameters on the control potential of the parasitoid Dinarmus basalis Rondani was investigated for high populations of larvae of Acanthoscelides obtectus (Say) feeding inside dry common bean seeds Phaseolus vulgaris. The beans were already infested with immature bruchids at the beginning of the storage period to simulate harvest conditions, characterized in a previous study. Treatments resulted in a reduction of 48-75% of the bruchid population within 16 weeks of storage. The best timing of parasitoid release was at the simulated harvest, as later releases reduced the bruchid population only by about half this percentage. Host feeding is postulated to be the key factor involved in the observed difference. The effect of increasing the number of parasitoids strongly depended on host age and food supplement. Addition of vials with honey had no direct effect on the bruchid population or on the parasitoid progeny. The ecological significance of these findings and implications for biological control are discussed.     

Ticks (Acari: Ixodoidea) in China: Geographical distribution,host diversity,and specificity

Ticks are obligate blood‐sucking ectoparasites, which not only directly damage through bites but also transmit many pathogens. China has a high diversity of tick species, 125 species have been reported, including 111 hard tick and 14 soft tick species. Many of the ticks are important vectors of pathogens, resulting in zoonoses. The dynamics of ticks are affected by both the host and habitat environment. However, systematic studies on the geographical distribution, host diversity, and specificity of ticks are limited in China. To achieve this goal, the relevant available data were summarized and analyzed in this study. Ticks are distributed in all parts of China and Xinjiang has the most records of ticks. The distribution of ticks in adjacent areas is similar, indicating that the habitat environment affects their distribution. Most ticks are widely distributed, whereas some species are endemic to their distributed regions. Ticks are parasitic on mammals, birds, and reptiles, of which mammals are the main host species. Overall, most ticks parasitize different hosts, only a few ticks have strict host specificity, such as ticks that are specifically parasitic on reptiles and bats. In addition, environmental changes and control efforts also influence the dynamics of ticks. These results can better reveal tick biological traits and are valuable for tick control.     

Diversity and host associations of parasitoids attacking mycophagous drosophilids (Diptera: Drosophilidae) in northern and central Japan

The diversity and host associations of parasitoids attacking mycophagous drosophilids were studied in Tokyo (a warm‐temperate region) and Sapporo (a cool‐temperate region) in Japan. Field collections were carried out using traps baited with mushrooms in May, June, September and October 2009 in Tokyo and in July and August 2010 in Sapporo. The major drosophilid species that emerged from mushroom baits was Drosophila bizonata in Tokyo and D. orientacea in Sapporo. In total, 13 parasitoid species emerged from drosophilids occurring in mushroom baits, and 11 of them were larval parasitoids belonging to Braconidae and Figitidae. Among the 11 larval parasitoids, 10 were collected in Tokyo, while only two were collected in Sapporo. It is not known why their diversity differed so much between these two regions. Four of the 11 larval parasitoids have also been recorded from drosophilid larvae occurring in fruit (banana). The use of these two habitats (mushrooms and fruit) by these four species seems to reflect the occurrence (i.e. resource use) of their suitable hosts. On the other hand, most larval parasitoids from Tokyo attacked D. bizonata, and two larval parasitoids from Sapporo attacked D. orientacea, suggesting that the abundance of potential hosts is one of the important factors affecting their host use.     

Unexpected diversity in the catfish Pseudancistrus brevispinis reveals dispersal routes in a Neotropical center of endemism: the Guyanas Region

Neotropical freshwater fishes have reached an unrivalled diversity, organized into several areas of endemism, yet the underlying processes are still largely unknown. The topographical and ecological characteristics of the Guyanas Region make it an ideal area of endemism in which to investigate the forces that have shaped this great diversity. This region is thought to be inhabited by species descending from Amazonian ancestors, which would have used two documented routes that, however, hardly explain the entrance of species adapted to running waters. Here, we investigate the evolutionary history of Pseudancistrus brevispinis , a catfish endemic to this region and exclusively found in running waters, thus making it an ideal model for investigating colonization routes and dispersal in such habitats. Our analyses, based on mitochondrial and nuclear markers, revealed an unexpected diversity consisting of six monophyletic lineages within P. brevispinis , showing a disjoint distribution pattern. The lineages endemic to Guyanas coastal rivers form a monophyletic group that originated via an ancestral colonization event from the Amazon basin. Evidence given favours a colonization pathway through river capture between an Amazonian tributary and the Upper Maroni River. Population genetic analyses of the most widespread species indicate that subsequent dispersal among Guyanas coastal rivers occurred principally by temporary connections between adjacent rivers during periods of lower sea level, yet instances of dispersal via interbasin river captures are not excluded. During high sea level intervals, the isolated populations would have diverged leading to the observed allopatric species. This evolutionary process is named the sea level fluctuation (SLF) hypothesis of diversification.