Taxonomy and conservation: a tale of two tinamou species groups (Tinamidae,Crypturellus)

Species delimitation has important consequences for the management of endangered species. Species‐level taxonomy in the genus Crypturellus (Tinamidae) has been based largely on plumage characters and species limits in several groups have been difficult to establish. Because some of the forms of uncertain taxonomic status are currently threatened with extinction, a basic understanding of species limits is crucial not only for taxonomists but also for conservation biologists and managers. We analysed vocal variation to assess species limits in two Crypturellus species‐groups, the red‐legged complex (Crypturellus erythropus and allied forms) and the brown tinamou Crypturellus obsoletus. In the red‐legged complex, where several species‐level taxa have been recognized by some authors, there is no obvious geographic variation in vocalizations and populations appear mostly continuously distributed, with plumage variation largely explicable in terms of environmental conditions. In the brown group, a single species is recognized, but we found marked geographic variation in vocalizations and populations have disjunct distributions; we propose that at least one of the populations in this group likely merits recognition as a separate species. We conclude that incomplete knowledge of patterns of variation in relevant traits in addition to the momentum carried by traditional taxonomy may potentially mislead conservation actions.     

A means of estimating the completeness of haplotype sampling using the Stirling probability distribution

I present a tool for use in phylogeography that helps estimate the completeness of haplotype sampling, based on the number of individuals analysed and the number of different haplotypes they show. Applying the Stirling probability distribution and Bayes’ theorem, a posterior probability distribution of the total number of haplotypes, including those yet to be observed, may be obtained. This enables one to deduce if the data are complete enough for further analysis. A program for calculating the posterior probabilities is available at http://www.botanik.univie.ac.at/plantchorology/haplo.htm .     

A field test of the directed deterrence hypothesis in two species of wild chili

The directed deterrence hypothesis posits that secondary metabolites in ripe fruit function to deter fruit consumption by vertebrates that do not disperse seeds, while not impacting consumption by those that do. We tested this hypothesis in two species of wild chilies (Capsicum spp.). Both produce fruits that contain capsaicinoids, the compounds responsible for the pungency of chilies. Previous work suggests seed-dispersing birds but not seed-destroying rodents consume chili fruits, presumably because rodents are deterred by capsaicin. However, fruit removal from chili plants by rodents and other mammals has not been previously explored. Because laboratory rodents can develop a preference for capsaicin, it is quite possible that wild rodents are natural consumers of chili fruits. We monitored the fate of 125 marked fruits of Capsicum chacoense and 291 fruits of Capsicum annuum. For both species, essentially all fruit removal occurred during the day, when rodents are inactive. Video monitoring revealed fruit removal only by birds, mostly by species known to disperse chili seeds in viable condition. Furthermore, these species are from taxonomic groups that tend to specialize on lipid-rich fruits. Both species of chili produce fruits that are unusually high in lipids (35% in C. chacoense, 24% in C. annuum). These results support the directed deterrence hypothesis and suggest that fruiting plants distinguish between seed predators and seed dispersers by producing fruits that repel the former and attract the latter.     

Reproductive biology and species geographical distribution in the Melastomataceae: a survey based on New World taxa

Background and Aims

Floral variation, pollination biology and mating patterns were investigated in sunbird-pollinated Babiana (Iridaceae) species endemic to the Western Cape of South Africa. The group includes several taxa with specialized bird perches and it has been proposed that these function to promote cross-pollination.

Methods

Pollinator observations were conducted in 12 populations of five taxa (B. ringens subspp. ringens, australis, B. hirsuta, B. avicularis, B. carminea) and geographic variation in morphological traits investigated in the widespread B. ringens. Experimental pollinations were used to determine the compatibility status, facility for autonomous self-pollination and intensity of pollen limitation in six populations of four taxa. Allozyme markers were employed to investigate mating patterns in four populations of three species.

Key Results

Sunbirds were the primary pollinators of the five Babiana taxa investigated. Correlated geographical variation in perch size, flower size and stigma–anther separation was evident among B. ringens populations. Experimental pollinations demonstrated that B. ringens and B. avicularis were self-compatible with variation in levels of autonomous self-pollination and weak or no pollen limitation of seed set. In contrast, B. hirsuta was self-incompatible and chronically pollen limited. Estimates of outcrossing rate indicated mixed mating with substantial self-fertilization in all species investigated.

Conclusions

Despite the possession of specialized bird perches in B. ringens and B. avicularis, these structures do not prevent considerable selfing from occurring, probably as a result of autonomous self-pollination. In eastern populations of B. ringens, smaller flowers and reduced herkogamy appear to be associated with a shift to predominant selfing. Relaxed selection on perch function due to increased selfing may explain the increased incidence of apical flowers in some populations.     

A classification of the New World species of Aster (Asteraceae)

In order effectively to list and comment on the results of cytological investigations inAster in a companion paper, a scheme of infrageneric classification is presented which utilizes the basic chromosome number as a pivotal diagnostic character. Reasons are stated as to why, with the exception ofUnamia Greene which is transferred toSolidago, and the commonly recognized generaLeucelene Greene,Machaeranthera Nees andXylorhiza Nutt., none of the segregate genera previously proposed or recorded in the literature is upheld. Instead, these taxa are being given subgeneric or sectional rank. Two additional subgenera are established to accommodate the species groups traditionally placed in “Aster proper,” which are characterized by having basic chromosome numbers ofx = 5 andx = 8, respectively. Altogether ten subgenera of the genusAster, five of them subdivided further into a total of 24 sections, are recognized as having representative species in the New World. All basionyms and type species are listed, and a number of new combinations and status changes are validated in accordance with the International Rules of Botanical Nomenclature. Where known (from literature and personal research), chromosome numbers are recorded for the species.     

Getting western: biogeographical analysis of morphological variation,mitochondrial haplotypes and nuclear markers reveals cryptic species and hybrid zones in the Junonia butterflies of the American southwest and Mexico

The American southwest and northern Mexico has a great degree of endemic diversity compared with the rest of North America. The Pleistocene glaciations and the dispersal of species from glacial refuges in this region have been important engines for the production of biodiversity in the region. The New World Junonia are a recent radiation of butterflies that are thought to have spent time in these refuges during periods of glacial advancement. We have reconstructed the plausible movements and the contemporary geographic distributions of the five taxa (J. coenia, J. grisea, J. litoralis, J. nigrosuffusa and J. zonalis) that occur in the American southwest and northern Mexico using phenotypic and genotypic information primarily from specimens preserved in museum collections, supplemented with additional contemporary collections. Evidence of cryptic species and hybridization events were observed using mitochondrial haplotypes, genotypic variation at the nuclear wingless locus, multilocus DNA fingerprinting, patterns of larval host plant use, variation in life‐history traits and morphological characteristics. Based on these lines of evidence, and in spite of low levels of hybridization between them, we argue that all five Junonia taxa are independent evolutionary lineages. Junonia grisea and J. coenia are morphologically very similar, but differences in morphology, life‐history traits, nuclear genotypes and mitochondrial haplotypes suggest that they are a cryptic species pair, thus elevating J. grisea comb.n. to a full species when it had previously been considered to be a subspecies of J. coenia.     

植物群落物种共存机制:负密度制约假说

负密度制约假说主要描述由于资源竞争、有害生物侵害(比如病原微生物、食草动物捕食)等, 同种个体之间发生的相互损害行为; 它主要强调同种个体之间的相互作用, 解释自然群落物种共存的机理; 负密度制约机制主要在小尺度上降低群落内同种个体生长率, 同时提高个体死亡率, 从而为其他物种的生存提供空间和资源, 促进物种共存。目前负密度制约假说的检验研究主要侧重密度制约、距离制约、群落补偿效应等三个方面。最近, 研究者又探讨了近缘物种之间由于对相似资源的竞争所产生的负效应, 扩展了负密度制约假说, 进而提出异群保护假说和谱系多样性制约假说。负密度制约假说引起生态学家长久的探讨和关注, 世界范围内大尺度森林动态样地的建立, 又为探索不同尺度上密度制约效应的研究提供了条件。然而目前的研究仍然存在不足, 比如负密度制约假说的检验受到其他因素的干扰、区域研究不平衡等。因此, 生态学家们仍然怀疑负密度制约效应调节群落物种共存的重要性, 但是目前的研究还没有发现否定负密度制约假说的充分证据。     

A tale of two snails: is the cure worse than the disease?

The giant African snail, Achatina fulica, has been introduced to many parts of Asia as well as to numerous islands in the Indian and Pacific Ocean, and has recently reached the West Indies. It has been widely decried as a disaster to agricultural economies and a threat to human health, leading to a clamor for the introduction of biological control agents. In fact, the lasting impact on agriculture may not be severe, and the human health risk is probably minor. This snail can be an aesthetic atrocity and a nuisance in other ways, however. Wherever A. fulica has achieved high densities, it has subsequently undergone a striking decline. Although this decline has been attributed to introduced predators, there is little evidence for this hypothesis; instead, epizootic disease seems to be at least part of the cause. However, the introduced predators, especially a New World snail, Euglandina rosea, have wrought havoc with the native land snails of many islands. They have already caused many extinctions and will almost certainly cause others. This predator was introduced by government agencies in many areas despite warnings from competent biologists that the effects could be disastrous. Pressures for such actions may become overwhelming in the face of a highly visible invasion, despite policies that should mandate extreme caution.     

Testing the divergent adaptation of two congeneric tree species on a rainfall gradient using eco‐physio‐morphological traits

In tropical Africa, evidence of widely distributed genera transcending biomes or habitat boundaries has been reported. The evolutionary processes that allowed these lineages to disperse and adapt into new environments are far from being resolved. To better understand these processes, we propose an integrated approach, based on the eco‐physio‐morphological traits of two sister species with adjacent distributions along a rainfall gradient. We used wood anatomical traits, plant hydraulics (vulnerability to cavitation, wood volumetric water content, and hydraulic capacitance), and growth data from the natural habitat, in a common garden, to compare species with known phylogeny, very similar morphologically, but occupying contrasting habitats: Erythrophleum ivorense (wet forest) and Erythrophleum suaveolens (moist forest and forest gallery). We identified some slight differences in wood anatomical traits between the two species associated with strong differences in hydraulics, growth, and overall species distribution. The moist forest species, E. suaveolens, had narrower vessels and intervessel pits, and higher vessel cell‐wall reinforcement than E. ivorense. These traits allow a high resistance to cavitation and a continuous internal water supply of the xylem during water shortage, allowing a higher fitness during drought periods, but limiting growth. Our results confirm a trade‐off between drought tolerance and growth, controlled by subtle adaptations in wood traits, as a key mechanism leading to the niche partitioning between the two Erythrophleum species. The generality of this trade‐off and its importance in the diversification of the African tree flora remains to be tested. Our integrated eco‐physio‐morpho approach could be the way forward.     

A test of the haploid susceptibility hypothesis using a species with naturally occurring variation in ploidy

The haploid susceptibility hypothesis (HSH) was proposed as an explanation for how behavioral roles in haplodiploid social systems evolved. It posits that haploid males are more susceptible to disease than diploid females due to decreased genetic variability at key disease resistance loci. The resulting decreased immunocompetence is hypothesized to have played a role in the evolution of social behavior by limiting the behavioral repertoire haploids perform. Here, we test this hypothesis in a study system that separates ploidy from behavioral sex roles: Polistes dominulus, a social wasp, has colonies with naturally occurring diploid males. We report results from two immune function assays—hemolymph phenoloxidase activity and encapsulation response—performed on haploid males, diploid males, and diploid females. Our data suggest that ploidy is not a significant contributor to immune function in P. dominulus; thus, our data do not support the HSH for the evolution of behavioral roles. Instead, our data indicate that time of emergence is the best predictor of immune function in Polistes. We speculate that seasonal trends result from seasonal differences in pathogens and parasites.