Species boundaries, specialization, and the radiation of sponge-dwelling alpheid shrimp

Microevolutionary studies and natural history suggest that host-specialization has promoted the high diversity of tropical sponge-dwelling snapping shrimps (Decapoda, Alpheidae, Synalpheus ). Yet the taxonomic difficulty of this genus has precluded rigorous tests of this hypothesis. S. rathbunae Coutiére is among the most abundant invertebrates inhabiting the framework of sponges and dead coral that forms the floor of Caribbean coral reefs. Even within a small area S. rathbunae exhibits the apparently wide variation in size, color, and morphology that has long frustrated efforts to identify and define species boundaries within this large (> 100 described species) genus. Here I show that sympatric populations of this nominal species occupying different sponge hosts display clear, concordant differences in allozyme genotypes and in multivariate morphometries, confirming that the populations represent three distinct biological species. Moreover, careful field sampling revealed that the three S. rathbunce taxa and the closely related S. filidigitus Armstrong showed almost no overlap in the species of hosts occupied. Interestingly, while there was significant differentiation between Belizean and Panamanian populations of the one taxon that occurred at both sites (∼1500 km apart), these populations were recognizable as conspecific using both genetic and morphological characters. These results show that (1) diversity of Synalpheus , which is already among the most species-rich crustacean genera, is probably several times higher than currendy recognized, and (2) species of sponge-dwelling Synalpheus are highly host-specific, with related species distinctly segregated among hosts. Together with previous evidence of host race differentiation within shrimp species, these results suggest a primary role for resource specialization in the origin and/or maintenance of this group's characteristically high diversity.     

Diversities of coral-associated bacteria differ with location, but not species, for three acroporid corals on the Great Barrier Reef

Patterns in the diversity of bacterial communities associated with three species of Acropora ( Acropora millepora, Acropora tenuis and Acropora valida ) were compared at two locations (Magnetic Island and Orpheus Island) on the Great Barrier Reef to better understand the nature and specificity of coral–microbial symbioses. Three culture-independent techniques demonstrated consistent bacterial communities among replicate samples of each coral species, confirming that corals associate with specific microbiota. Profiles were also conserved among all three species of Acropora within each location, suggesting that closely related corals of the same genus harbor similar bacterial types. Bacterial community profiles of A. millepora at Orpheus Island were consistent in samples collected throughout the year, indicating a stable community despite temporal changes. However, DGGE and T-RFLP profiles differed on corals from different reefs. Nonmetric multidimensional scaling of T-RFLP profiles showed that samples grouped according to location rather than coral species. Although similar sequences were retrieved from clone libraries of corals at both Magnetic and Orpheus Island, differences in the relative dominant bacterial ribotypes within the libraries drive bacterial community structure at different geographical locations. These results indicate certain bacterial groups associated specifically with corals, but the dominant bacterial genera differ between geographically-spaced corals.     

Scarid Biomass on the Northern Great Barrier Reef: The Influence of Exposure, Depth and Substrata

Here I investigate whether patterns of scarid biomass across the continental shelf of the northern Great Barrier Reef can be explained by species associating with particular characteristics of the reef environment. Despite the widely documented tendency of scarids to graze and browse over exposed calcareous reef surfaces, scarid biomass was not significantly correlated with the availability of feeding substrata for any species investigated. Indeed positive correlations between biomass and substrata variables were rare for the 18 species investigated, indicating that biomass in these taxa was not strongly reliant on the availability of preferred substrata quantified at the spatial scale of sites (1620m²). Rather, species specific biomass was commonly highly variable between sites, suggesting that local aggregation of scarids commonly occurs at this scale. Such spatial patchiness potentially reflects the effects of spatially variable recruitment, fishes associating with unmeasured habitat characteristics or aggregating prior to spawning. Despite variability in the biomass of individual species between replicate sites within exposure regimes, exposure was generally a far more reliable predictor of biomass than the other variables quantified. This study provides little evidence to indicate that adult scarids have strict habitat requirements, rather they appear to be habitat generalists whose biomass is strongly influenced by exposure but weakly related to the cover of particular reef substratum.     

Geographic differences in species boundaries among members of the Montastraea annularis complex based on molecular and morphological markers

The three members of the Montastraea annularis complex (M. annularis, M. franksi, and M. faveolata) are dominant reef builders in the western Atlantic whose species status has been controversial for over a decade. Although differences in colony morphology and reproductive characteristics exist, interspecific fertilizations are possible in the laboratory and genetic differentiation is slight. Here we compare the three taxa genetically and morphologically in Panama and the Bahamas, widely separated locations spanning most of their geographic ranges. In Panama, analyses of three AFLP loci, a noncoding region of the mitochondrial genome, and ITS sequences reveal that M. faveolata is strongly differentiated genetically. Discriminant function analysis also indicates no overlap with the other two species in the fine structure of the corallites that comprise the colony. Genetic analyses of larvae from interspecific crosses between M. faveolata and the other two taxa confirmed the hybrid status of the larvae, but no examples of the most probable F1 genotype were observed in the field. Although M. annularis and M. franksi were more similar, they also exhibited strong frequency differences at two AFLP loci and in the mitochondrial noncoding region, as well as distinct corallite structure. In the Bahamas, in contrast, the three taxa exhibited overlapping morphologies. Montastraeafranksi and M. annularis were indistinguishable genetically, and M. faveolata was distinct at fewer genetic loci. Once again, however, the most probable F1 genotype involving M. faveolata was not observed. Geographic differences between Panama and the Bahamas explain why past studies have come to different conclusions concerning the status of the three species. In general, the genetic and morphological data suggest a north to south hybridization gradient, with evidence for introgression strongest in the north. However, reproductive data show no such trend, with intrinsic barriers to gene flow comparable or stronger in the north.     

Cryptic diversity,high host specificity and reproductive synchronization in army ant‐associated Vatesus beetles

Army ants and their arthropod symbionts represent one of the most species‐rich animal associations on Earth, and constitute a fascinating example of diverse host–symbiont interaction networks. However, despite decades of research, our knowledge of army ant symbionts remains fragmentary due to taxonomic ambiguity and the inability to study army ants in the laboratory. Here, we present an integrative approach that allows us to reliably determine species boundaries, assess biodiversity, match different developmental stages and sexes, and to study the life cycles of army ant symbionts. This approach is based on a combination of community sampling, DNA barcoding, morphology and physiology. As a test case, we applied this approach to the staphylinid beetle genus Vatesus and its different Eciton army ant host species at La Selva Biological Station, Costa Rica. DNA barcoding led to the discovery of cryptic biodiversity and, in combination with extensive community sampling, revealed strict host partitioning with no overlap in host range. Using DNA barcoding, we were also able to match the larval stages of all focal Vatesus species. In combination with studies of female reproductive physiology, this allowed us to reconstruct almost the complete life cycles of the different beetle species. We show that Vatesus beetles are highly adapted to the symbiosis with army ants, in that their reproduction and larval development are synchronized with the stereotypical reproductive and behavioural cycles of their host colonies. Our approach can now be used to study army ant‐symbiont communities more broadly, and to obtain novel insights into co‐evolutionary and ecological dynamics in species‐rich host–symbiont systems.     

Taxonomy, host specificity and dietary implications of Hurleytrematoides (Digenea: Monorchiidae) from chaetodontid fishes on the Great Barrier Reef

Five new and five previously described species of Hurleytrematoides are reported from 19 of 34 chaetodontid species examined from the Great Barrier Reef; new species are H. faliexae n. sp., H. galzini n. sp., H. loi n. sp., H. morandi n. sp., and H. sasali n. sp. Previously described species are H. coronatum, H. fijiensis, H. prevoti, H. bartolii, and H. zebrasomae. The genus is rediagnosed in the light of morphological variation of the new species; the degree of spination and shape of the terminal genitalia distinguish individual species. Species of Hurleytrematoides infect almost every clade of the family Chaetodontidae found on the Great Barrier Reef, but obligate corallivores are not infected. All ten species were found at Heron Island on the southern Great Barrier Reef, but only six at Lizard Island on the northern Great Barrier Reef. For three of the four species not present at Lizard Island, the absence appears to be statistically significant. Although all species are apparently restricted to chaetodontids on the GBR, specificity within the family varies from oioxenous to euryxenous; a core/satellite host paradigm explains the distribution of several species.     

The effect of the taxon and geographic range size of host eucalypt species on the species richness of gall-forming insects

Abstract This field study was designed to test whether the taxonomic group and geographic range size of a host plant species, usually found to influence insect species richness in other parts of the world, affected the number of gall species on Australian eucalypts. We assessed the local and regional species richness of gall-forming insects on five pairs of closely related eucalypt species. One pair belonged to the subgenus Corymbia, one to Monocalyptus, and three to different sections of Symphyomyrtus. Each eucalypt pair comprised a large and a small geographic range species. Species pairs were from coastal or inland regions of eastern Australia. The total number of gall species on eucalypt species with large geographic ranges was greater than on eucalypt species with small ranges, but only after the strong effect of eucalypt taxonomic grouping was taken into account. There was no relationship between the geographic range size of eucalypt species and the size of local assemblages of gall species, but the variation in insect species composition between local sites was higher on eucalypt species with large ranges than on those with small ranges. Thus the effect of host plant range size on insect species richness was due to greater differentiation between more widespread locations, rather than to greater local species richness. This study confirms the role of the geographic range size of a host plant in the determination of insect species richness and provides evidence for the importance of the taxon of a host plant.     

Patterns of host utilisation by herbivore assemblages of the genus Caloptilia (Lepidoptera; Gracillariidae) on congeneric maple tree (Acer) species

1. The pattern of host utilisation by congeneric Caloptilia caterpillars on 14 different species of Acer (maple) was investigated in temperate mixed forests of central Japan. A multi‐filtering model of host plant utilisation was proposed to address how phylogenetically related herbivore assemblages are constructed on phylogenetically related host plant species. 2. Two hypotheses were examined. The first questioned whether a negative relationship exists between the phylogenetic distance of plants from the most suitable host species and the abundance of herbivorous insects on the host. Regarding the second, it was investigated whether the assemblage dissimilarity of herbivorous insects among host plant species increases with increasing distance of plant phylogeny and traits. 3. Mantel and partial Mantel tests were used to measure the relationship between assemblage dissimilarity of Caloptilia species and the distance of plant phylogeny and leaf traits. 4. Both hypotheses were confirmed, clearly suggesting that the utilisation and suitability of hosts for Caloptilia caterpillars were strongly influenced by phylogenetic relatedness and leaf trait similarity among Acer species. This implies that phylogenetic distance is an integrated measure of phenotypic and ecological attributes of congeneric Acer species that can be used to explain specialisation and constraints of host utilisation of congeneric herbivore species even on a short evolutionary timescale.     

Determinants of ectoparasite assemblage structure on rodent hosts from South American marshlands: the effect of host species,locality and season

The relative effects of host species identity, locality and season on ectoparasite assemblages (relative abundances and species richness) harboured by four cricetid rodent hosts (Akodon azarae, Oligoryzomys flavescens, Oxymycterus rufus and Scapteromys aquaticus) were assessed across six closely located sites in Buenos Aires province, Argentina. Relative abundances of ectoparasites (14 species including gamasid mites, an ixodid tick, a trombiculid mite, lice and fleas), as well as total ectoparasite abundance and species richness, were determined mainly by host species and to a lesser extent by locality (despite the small spatial scale of the study), whereas seasonal effect was weak, albeit significant. The abundances of some ectoparasites were determined solely by host, whereas those of other ectoparasites (sometimes belonging to the same higher taxon) were also affected by locality and/or season. In gamasids, there was a significant effect of locality for some species, but not for others. In fleas and lice, the effect of locality was similar in different species, suggesting that this effect is related to the characteristic life history strategy.     

盆栽榕树蓟马种类及优势种榕管蓟马对寄主植物的致害性

为明确盆栽榕树蓟马的种类, 了解蓟马优势种对在同一温室内混合种植的榕属及非榕属盆栽植物的致害性差异, 以福建漳州、 福州和泉州等地的盆栽榕树种植基地为观测点, 采集榕树叶片, 调查蓟马种类, 确定优势种蓟马; 以天南星科喜林芋属、 紫葳科菜豆树属、 木棉科瓜栗属和桑科榕属等不同科属盆栽植物为试验材料, 测试榕管蓟马Gynaikothrips uzeli Zimmerman对寄主植物的致害性。结果表明： 盆栽榕树蓟马种类有2亚目, 2科, 8属, 9种, 优势种为榕管蓟马, 常见种为棘腿管蓟马Androthrips ramachandrai Karny和榕腿管蓟马Mesothrips jordani Zimmermann, 其他6种蓟马均为偶见种。榕管蓟马对不同寄主植物的致害性差异显著, 以对桑科榕属植物致害性为最强, 而对天南星科喜林芋属、 紫葳科菜豆树属和木棉科瓜栗属等其他植物的致害性较弱。在6种榕属植物中, 榕管蓟马对垂叶榕Ficus benjamina Linn.、 榕树F. microcarpa Linn. f.、 花叶垂叶榕F. benjamina cv. Golden Princess等3种榕属植物的为害等级均达3级以上, 以垂叶榕最重, 榕树次之, 花叶垂叶榕略轻; 对金叶榕F. microcarpa cv. Golden Leaves、 黑叶橡胶榕F. elastica cv. Deocora Burgundy、 斑叶橡胶榕F. elastica var. variegata等3种榕属植物的为害很轻, 为害等级均仅为1级; 同时, 榕管蓟马在金叶榕、 黑叶橡胶榕和斑叶橡胶榕上繁殖力弱、 无法完成世代, 而在榕树、 垂叶榕和花叶垂叶榕上繁殖力强、 能完成世代, 但以在垂叶榕上的发育情况最好。研究可为选择利用寄主植物抗虫性来有效防控盆栽榕树蓟马提供技术支撑。     

The impact of redefined species limits in Palame (Coleoptera: Cerambycidae: Lamiinae: Acanthocinini) on assessments of host, seasonal, and stratum specificity

Assumptions about the host and stratum specificity of tropical insects are routinely incorporated into estimates of global species richness, but few empirical studies reliably assess tropical insect specificity. In French Guiana, cerambycid beetles in the genus Palame reproduce exclusively in trees belonging to the Brazil nut family (Lecythidaceae). During a year-long rearing project, Palame anceps (Bates) emerged exclusively from a single host species, but P. crassimana Bates and P. mimetica Monné appeared to make seasonal changes in host affiliation. In the case of P. crassimana , dry season specimens could be distinguished from rainy season specimens by subtle differences in pubescence, but it was difficult to find diagnostic morphological characters supporting their delimitation as separate species. In order to detect genetic differentiation in Palame , 1049 bp of mitochondrial DNA (COI gene) were sequenced. The three nominal species of Palame yielded six haplotype groups, with sequence divergences among groups ranging from 8.27 to 17.56%. Species with apparent seasonal changes in host use included multiple distinct haplotype groups that I interpret to represent multiple species-level taxa. Insects considered generalized owing to temporal or geographical changes in host association may, with improved resolution in species limits, prove to be assemblages including relatively specialized cryptic species. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 195–209.     

Phylogeny‐based species delimitations and the evolution of host associations in symbiotic zoanthids (Anthozoa,Zoanthidea) of the wider Caribbean region

Zoanthids are marine cnidarians with simple morphologies that challenge our ability to delineate species. Phylogenetic analyses of internal transcribed spacer (ITS) sequences are consistent with six morphologically described species from the wider Caribbean region, and reveal four additional species that were not previously recognized. Histological examinations of unidentified species reveal cryptic Isozoanthus and Edwardsiidae (Actiniaria) species. Observations of zoanthids in situ reveal geographic distributions that range from regional to trans‐Atlantic. ITS and 16S data are consistent with hypotheses of paraphyly in some higher taxa of zoanthids; however, the clades of zoanthids recovered in both analyses can largely be defined by their host associations, thereby supporting phylogenetic conservatism in zoanthid–host association evolution. The single clear example of a zoanthid switching hosts was accompanied by a compensatory loss of endosymbiosis, which maintained the match in photosynthetic symbioses between zoanthids and sponge hosts. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 223–238.     

Influence of species of host plants on the predation of thrips by Neoseiulus cucumeris, Iphiseius degenerans and Orius laevigatus

A leaf-disc bioassay was used to compare the predation levels of two species of predatory mites (Neoseiulus cucumeris (Oudemans) and Iphiseius degenerans (Berlese)) and a predatory bug (Orius laevigatus (Fieber)), on the thrips Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouché), feeding on a range of susceptible plant species from twelve plant families. The predatory bug, O. laevigatus, reduced the number of thrips to a greater extent than the predatory mites and all three predators showed greater levels of predation on F. occidentalis than on H. haemorrhoidalis. The level of predation caused by each predator varied among the species of plants; the variation was greater on the plant hosts of H. haemorrhoidalis than of F. occidentalis.     

Effect of host plant,prey species and intergenerational changes on the prey preferences of the predatory mirid <Emphasis Type="Italic">Macrolophus caliginosus</Emphasis>

The outdoor establishment of non-native biocontrol agents released for inundative control of glasshouse pests is determined primarily by two factors: ecophysiological compatibility with local climate, particularly winter cold tolerance, and ability to locate and utilise wild prey. Observations on the number and diversity of acceptable wild prey as part of an assessment of establishment potential therefore overlap with more focused studies to determine host range. This study investigated two aspects of the interactions between biocontrol agents and non-target prey that are rarely considered in tests for establishment or host range: the role of different host plant–prey associations in modifying the development and reproduction of biocontrol agents, and the longer term sustainability of such relationships beyond the single generation observed in most laboratory studies. Using the glasshouse whitefly (Trialeurodes vaporariorum) predator Macrolophus caliginosus Wagner (Hemiptera: Miridae) as a case study, the mirid was able to sustain viable populations over three generations on the related cabbage whitefly Aleyrodes proletella (Linnaeus) (Hemiptera: Aleyrodidae) and the aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae), including when these prey were feeding on different host plants (Chinese cabbage, cabbage and Brussels sprout). However, the rate of development, fecundity and mortality of the predator varied between the different prey and host plant combinations, and in all cases differed than when feeding on its glasshouse prey T. vaporariorum reared on tobacco (Nicotiana tabacum). The results are discussed in the light of the current debate on methods for conducting host range testing as part of an environmental risk assessment. Handling Editor: Dirk Babendreier     

Post-release survey to assess impact and potential host range expansion by Amitus hesperidum and Encarsia perplexa, two parasitoids introduced for the biological control of the citrus blackfly, Aleurocanthus woglumi in Dominica

Four years after the release of two exotic parasitoids, Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) and Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) for the classical biological control of the citrus blackfly (CBF), Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) in Dominica, a survey was conducted to assess establishment as well as potential nontarget effects especially on Aleyrodidae and other related taxa. CBF populations were low to non-existent in 50 of 51 field sites examined. At the site where CBF was encountered, both E. perplexa and A. hesperidum were present and CBF populations were declining. The two parasitoids were not among the several species collected on nontarget Aleryodidae and Hemiptera. It is concluded that E. perplexa and A. hesperidum have kept CBF populations under effective biological control in Dominica and there is no evidence of any nontarget effects on other Aleyrodidae or their natural enemies. Handling Editor: Dirk Babendreier.     

Effects of nitrogen supply on the anatomy and chemical composition of leaves of four grass species belonging to the genus Poa, as determined by image-processing analysis and pyrolysis–mass spectrometry

Previous experiments have shown that the anatomy and chemical composition of leaves of inherently fast- and slow-growing grass species, grown at non-limiting nitrogen supply, differ systematically. The present experiment was carried out to investigate whether these differences persist when the plants are grown at an intermediate or a very low nitrogen supply. To this end, the inherently fast-growing Poa annua L. and Poa trivialis L., and the inherently slow-growing Poa compressa L. and Poa pratensis (L.) Schreb. were grown hydroponically at three levels of nitrate supply: at optimum (RGR_max) and at relative addition rates of 100 and 50 mmol N (mol N)^?1 d^?1 (RAR₁₀₀ and RAR₅₀), respectively. As expected, at the lowest N supply, the potentially fast-growing species grew at the same rate as the inherently slow-growing ones. Similarly, the differences in leaf area ratio (LAR, leaf area:total dry mass), specific leaf area (SLA, leaf arear:leaf dry mass) and leaf mass ratio (LMR, leaf dry mass:total dry mass) disappeared. Under optimal conditions, the fast-growing species differed from the slow-growing ones in that they had a higher N concentration. There were no significant differences in C concentration. With decreasing N supply, the total N concentration decreased and the differences between the species disappeared. The total C concentration increased for the fast-growing species and decreased for the slow-growing ones, i.e. the small, but insignificant, difference in C concentration between the species at RGR_max increased with decreasing N supply. The chemical composition of the leaves at low N supply, analysed in more detail by pyrolysis–mass spectrometry, showed an increase in the relative amounts of guaiacyl lignin, cellulose and hemicellulose, whereas those of syringyl lignin and protein decreased. The anatomy and morphology of the leaves of the four grass species differing in RGR_max were analysed by image-processing analysis. The proportion of the total volume occupied by mesophyll plus intercellular spaces and epidermis did not correlate with the amount of leaf mass per unit leaf area (specific leaf mass, SLM) at different N supply. The higher SLM at low N supply was caused partly by a high proportion of non-veinal sclerenchymatic cells per cross-section and partly by the smaller volume of epidermal cells. We conclude that the decrease in relative growth rate (and increase in SLM) at decreasing N supply is partly due to chemical and anatomical changes. The differences between the fast- and slow-growing grass species at an optimum nutrient supply diminished when plants were growing at a limiting nitrogen supply.