Small Proportion Of Species Research Articles

Species ethnobotanical values rather than regional species pool determine plant diversity in agroforestry systems

The conversion of natural systems into farms and agroecosystems is the main cause of biodiversity loss. In human-dominated landscapes, understanding the interactions between agroforestry systems and adjacent natural vegetation is fundamental to developing sustainable agricultural systems. Species can move between these two systems with natural systems providing the regional pool of species that shape the agricultural values and conservation value of the agroforestry systems. We investigated the influence of neighboring natural habitats on traditional agroforestry systems in the buffer zone of Pendjari Biosphere Reserve in Benin to understand the contribution of regional processes on the quality of agroforestry systems. We expected that agroforestry parklands adjacent to natural vegetation with high species diversity will also have higher plant species diversity. We found no similarity in plant species composition between agroforestry systems and adjacent natural habitats. A small proportion of species in adjacent natural habitats were found in agroforestry systems. The proportion of shared species was not significantly influenced by plant diversity in adjacent natural habitats or the distance from the agroforestry systems to the natural adjacent habitat. However, plant diversity in agroforestry systems was strongly associated with site ethnobotanical values indicating that farmers act as a supplemental but severe environmental filter of the regional species pool. Our study suggests that promoting the plantation of plants with high ethnobotanical use-value is a potentially viable strategy for sustainable agriculture and ecological restoration in Biosphere reserves.

Gymnosperm Resprouting—A Review

Gymnosperms are generally regarded as poor resprouters, especially when compared to angiosperms and particularly following major disturbance. However, is it this clear-cut? This review investigates two main aspects of gymnosperm resprouting: (i) various papers have provided exceptions to the above generalization—how frequent are these exceptions and are there any taxonomic trends?; and (ii) assuming gymnosperms are poor resprouters are there any anatomical or physiological reasons why this is the case? Five of six non-coniferous gymnosperm genera and 24 of 80 conifer genera had at least one species with a well-developed resprouting capability. This was a wider range than would be expected from the usual observation ‘gymnosperms are poor resprouters’. All conifer families had at least three resprouting genera, except the monospecific Sciadopityaceae. Apart from the aboveground stem, buds were also recorded arising from more specialised structures (e.g., lignotubers, tubers, burls and underground stems). In some larger genera it appeared that only a relatively small proportion of species were resprouters and often only when young. The poor resprouting performance of mature plants may stem from a high proportion of apparently ‘blank’ leaf axils. Axillary meristems have been recorded in a wide range of conifer species, but they often did not form an apical dome, leaf primordia or vascular connections. Buds or meristems that did form often abscised at an early stage. While this review has confirmed that conifers do not resprout to the same degree as angiosperms, it was found that a wide diversity of gymnosperm genera can recover vegetatively after substantial disturbance. Further structural studies are needed, especially of: (i) apparently blank leaf axils and the initial development of axillary meristems; (ii) specialised regeneration structures; and (iii) why high variability can occur in the resprouting capacity within species of a single genus and within genera of the same family.

Taxonomic reassessment of large mammals from the Pleistocene Homo-bearing site of Tham Wiman Nakin (Northeast Thailand): relevance for faunal patterns in mainland Southeast Asia

Tham Wiman Nakin or “Snake Cave” has so far been recognized as being the only late Middle Pleistocene Homo-bearing fauna, dated to older than 169 ka, in mainland Southeast Asia. Since the last two decades, the highly diversified mammal fauna found from this cave has been widely used as standard references for several studies, though the majority of fossil primates, carnivores, and ungulates have never been described in detail. This paper presents taxonomic descriptions of unpublished fossil specimens from the long-known collection of Tham Wiman Nakin. As a result, the fauna of Tham Wiman Nakin consisted of at least 28 large mammal taxa. Although several previously described specimens are re-assigned to different tooth elements and/or mammal taxa, our taxonomic study confirms the existence of most of the species identified from the previous work and describes three additional taxa for the locality: an Asian badger, a tiger, and a Himalayan goral. The Tham Wiman Nakin fauna is one of the most diverse Pleistocene mammals, including a hominin, in mainland Southeast Asia and documents long-term survivors of living species since the late Middle Pleistocene. Based on several recent dates of fossil sites in mainland Southeast Asia, biochronological data imply a possible faunal age up to the maximum of 300 ka for the Tham Wiman Nakin fauna, but younger than that of Pha Bong where Gigantopithecus was present. Fossil records in the region also suggest a relatively stable fauna through Pleistocene glacial-interglacial cycles, at least from the late Middle to latest Pleistocene. The extinction occurring in the mainland varied across taxa and likely resulted in less impacted biodiversity loss prior to the Holocene, compared to other continents, as indicated by the small proportion of species becoming extinct during each interval. The importance of stable mosaic habitats through time may provide clues to the long-term survival of several large mammal taxa in the region.

Species richness is a surrogate for rare plant occurrence, but not conservation value, in boreal plant communities

Rare species are an ecologically important component of biological communities, but may be at risk of decline as a result of human disturbance and other sources of environmental change. Rare species are also ecologically idiosyncratic, making their occurrence difficult to predict a priori, and leading to efforts to find surrogate measures of rare species occurrence to inform conservation decisions. Using floristic data collected at 602 sites in the western Canadian boreal forest, we studied relationships between rare species occurrence, species richness and habitat type, with rarity defined according to the classification system developed by Rabinowitz (in: Synge (ed) The biological aspects of rare plant conservation, Wiley, Somerset, 1981). Relative to similar studies in other temperate regions, we found that a smaller proportion of species were classified as rare in our study region, and that common species dominate the flora. Regional-scale relationships were positive between richness and the occurrence of rare species; however, due to variation in these relationships among habitat types, richness is not a suitable surrogate for a site’s conservation value with respect to species rarity.

Evolution of acoustic communication in European gobies (Gobius lineage) based on molecular markers

Evolution of acoustic communication in European gobies (Gobius lineage) based on molecular markers

Ecosystem engineering through aardvark (Orycteropus afer) burrowing: Mechanisms and effects

Burrowing mammals are often considered to be ecosystem engineers as burrowing disturbs the soil, thereby potentially changing resource availability and affecting habitat conditions for other species. After their excavation, burrows may strongly impact local plant communities through several mechanisms, including resource trapping, altered chemical and physical soil properties, and amelioration of microclimatic conditions. We studied ecosystem engineering by aardvark (Orycteropus afer) burrowing by comparing soil and vegetation characteristics between three microsites (burrow entrances, excavated soil mounds and adjacent control sites). We were able to identify several engineering effects and distinguish between potential mechanisms. Burrow soils were cooler, drier and less compact than the other microsites, with all three microsites representing unique combinations of abiotic conditions. Mean species richness was higher at older burrows than mounds and non-burrowed controls, despite burrows having a smaller seedbank and not differing in soil fertility from mounds and control sites. However, the opposite was observed at fresh burrows and mounds, where control plots contained more species on average than the other two types of microsites. Burrow age and microsite type also affected species composition, although only a small proportion of species were significantly associated with specific microsites and just two species were limited to a single microsite type. We suggest that trampling and the physical digging action at burrow entrances, and burial by deposited soil at mounds, prevents the establishment of many plant species at active burrows. However, once abandoned, burrow entrances provide good physical conditions for seedling survival, allowing the establishment of more species. Therefore, as suggested previously for other ecosystem engineers, it is important to explicitly consider the age and degradation processes of engineered structures. In addition, our results highlight biologically-important differences in engineering impacts between burrow entrances, where soil is removed, and mounds, where soil is deposited. Such microscale differences are important to consider when examining bioturbation or, more generally, ecosystem engineering.

Using intra-flock association patterns to understand why birds participate in mixed-species foraging flocks in terrestrial habitats

Bird species are hypothesized to join mixed-species flocks (flocks hereon) either for direct foraging or anti-predation-related benefits. In this study, conducted in a tropical evergreen forest in the Western Ghats of India, we used intra-flock association patterns to generate a community-wide assessment of flocking benefits for different species. We assumed that individuals needed to be physically proximate to particular heterospecific individuals within flocks to obtain any direct foraging benefit (flushed prey, kleptoparasitism, copying foraging locations). Alternatively, for anti-predation benefits, physical proximity to particular heterospecifics is not required, i.e. just being in the flock vicinity can suffice. Therefore, we used choice of locations within flocks to infer whether individual species are obtaining direct foraging or anti-predation benefits. A small subset of the bird community (5/29 species), composed of all members of the sallying guild, showed non-random physical proximity to heterospecifics within flocks. All preferred associates were from non-sallying guilds, suggesting that the sallying species were likely obtaining direct foraging benefits either in the form of flushed or kleptoparasitized prey. The majority of the species (24/29) chose locations randomly with respect to heterospecifics within flocks and, thus, were likely obtaining antipredation benefits. In summary, our study indicates that direct foraging benefits are important for only a small proportion of species in flocks and that predation is likely to be the main driver of flocking for most participants. Our findings apart, our study provides methodological advances that might be useful in understanding asymmetric interactions in social groups of single and multiple species.

Notas sobre las especies de los pastizales entre Iquitos y Nauta, Loreto, Perú

During the year 2006 were collected species of the grassland near the road between Iquitos and Nauta. We identified 69 species. The vegetation that characterizes this region is tropical rainforest, where the lower stratum is occupied by pastures consisting mainly of true grasses (Poaceae) and small proportion of species from other families such as Fabaceae, Malvaceae, Acanthaceas, Amaranthaceas, etc. We present keys for the identifica- tion of families, genera and species.

Life history, diversity and distribution: a study of Japanese pteridophytes

Many studies address the relationships between diversity or distribution and attributes of the physical environment. However, how these relationships are connected to variation in life history is poorly understood. This is particularly true in the case of pteridophytes. Japanese ferns and their allies comprise one of the best‐known pteridophyte floras in the world. We analyzed ca 600 species of Japanese pteridophytes for which there is detailed information on distribution, reproduction, and chromosome number. Species richness was greatest in groups with a single reproductive mode (sexual, followed by apogamous), but distribution was greatest in species groups with multiple reproductive modes: sexual plus either sterile (irregular in meiosis) or apogamous. Geographical ranges varied greatly among species with small chromosome numbers but were uniformly small among species having high chromosome numbers. Seasonally green (mostly summer green) species had significantly larger distribution ranges than evergreen species. Endemic species had higher proportions of apogamy and sterility than non‐endemic species. Seasonally green species had significantly larger distributional ranges, and a smaller proportion of species with apogamous reproduction, than evergreen species. There was no clear relationship between distribution and spore size, either among endemic species, non‐endemic species, or all species combined. There was no relationship between spore size and chromosome number when all species were combined. However, positive relationships were detected within three of the nine largest genera, suggesting potential phylogenetic effects. We concluded that habitat availability, rather than dispersability, may be the limiting factor for the distribution of pteridophytes in Japan.

An investigation of the Encrinurinae (Trilobita) by numerical taxonomic methods

SynopsisNumerical taxonomic methods are applied to the Encrinurinae (Trilobita). Thirty-five cranidial and pygidial attributes are defined of which some (e.g. those relating to the glabellar tubercles) are specific to encrinurines and cybelines while others have application to non-encrinurids. Of nearly 200 named species of Encrinurinae only about one-third have been described in the literature in sufficient detail for their cranidial and pygidial attribute states be coded: a much smaller proportion of species is well enough known for librigenal, rostral, hypostomal and thoracic attributes to be coded. A comprehensive numerical taxonomy of the subfamily must therefore await detailed description of most of the known species. A list is given of encrinurine species in need of re-investigation. Meanwhile, 63 species can be coded for 34 attributes, and 75 species for 28 attributes. Principal components analysis is used to produce ordinations of these species. The minimal spanning tree superimposed on the ordination suggests possible evolutionary lineages. Ordination of the attributes is by non-linear mapping based on a distance matrix derived from the inter-attribute correlation matrix by the transformation (tanh−1|r|)−1. The ordinations compare well with subjective assessments of relations and phylogenies.