Şerban Procheş

INTERACTIONS BETWEEN ENVIRONMENT, SPECIES TRAITS, AND HUMAN USES DESCRIBE PATTERNS OF PLANT INVASIONS

Although invasive alien species (IAS) are a major threat to biodiversity, human health, and economy, our understanding of the factors controlling their distribution and abundance is limited. Here, we determine how environmental factors, land use, life-history traits of the invaders, residence time, origin, and human usage interact to shape the spatial pattern of invasive alien plant species in South Africa. Relationships between the environmental factors and the extrinsic and intrinsic attributes of species were investigated using RLQ analysis, a multivariate method for relating a species-attribute table to an environmental table by way of a species presence/absence table. We then clustered species according to their position on the RLQ axes, and tested these groups for phylogenetic independence. The first three axes of the RLQ explained 99% of the variation and were strongly related to the species attributes. The clustering showed that, after accounting for environmental factors, the spatial pattern of IAS in South Africa was driven by human uses, life forms, and reproductive traits. The seven clusters of species strongly reflected geographical distribution, but also intrinsic species attributes and patterns of human use. Two of the clusters, centered on the genera Acacia and Opuntia, were phylogenetically non-independent. The remaining clusters comprised species of diverse taxonomic affinities, but sharing traits facilitating invasion in particular habitats. This information is useful for assessing the extent to which the potential spread of recent introductions can be predicted by considering the interaction of their biological attributes, region of origin, and human use.

The World's Zoogeographical Regions Confirmed by Cross-Taxon Analyses

The worlds zoogeographical regions were historically defined on an intuitive basis, with no or a limited amount of analytical testing. Here, we aimed (a) to compare analytically defined global zoogeographical clusters for the herpetofauna, birds, mammals, and all these groups taken together (tetrapod vertebrates); (b) to use commonalities among these groups to propose an updated global zoogeographical regionalization; and (c) to describe the resulting regions in terms of vertebrate diversity and characteristic taxa. The clusters were remarkably uniform across taxa and similar to previous intuitively defined regions. Eleven vertebrate-rich (Nearctic, Caribbean, Neotropical, Andean, Palearctic, Afrotropical, Madagascan, Indo-Malaysian, Wallacean, New Guinean, Australian) and three vertebrate-poor (Arctic, Antarctic, Polynesian) zoogeographical regions were derived; the Neotropical, Afrotropical, and Australian had the highest numbers of characteristic tetrapod genera. This updated regionalization provides analytically accurate divisions of the world, relevant to conservation, biogeographical research, and geography education.

Dissecting the plant–insect diversity relationship in the Cape

It has been argued that insect diversity in the Cape is disproportionately low, considering the unusually high plant diversity in this region. Recent studies have shown that this is not the case, but the precise mechanisms linking plant diversity and insect diversity in the Cape are still poorly understood. Here we use a dated genus-level phylogenetic tree of the Cape plants to assess how plant phylogenetic diversity compares with taxonomic diversity at various levels in predicting insect diversity. We find that plant phylogenetic diversity (PD) is a better predictor of insect species diversity that plant species diversity, but the number of plant genera is overall as good a predictor as PD, and much easier to calculate. The relationship is strongest between biomes, suggesting that the relationship between plant diversity and insect diversity is to a large extent indirect, both variables being driven by the same abiotic factors and possibly by common diversification, immigration and extinction histories. However, a direct relationship between plant diversity and insect diversity can be detected at fine scales, at least within certain biomes. Diversity accumulation curves also indicate that the way plant phylogenetic diversity and the number of plant genera increase over spatial scales is most similar to that for insect species; plant species show a greater increase at large spatial scales due to high numbers of local endemics.

How much evolutionary history in a 10×10 m plot?

We use a fully dated phylogenetic tree of the angiosperm families to calculate phylogenetic diversity (PD) in four South African vegetation types with distinct evolutionary histories. Since the branch length values are in this case represented by the ages of plant lineages, PD becomes the cumulative evolutionary age (CEA) of assemblages. Unsurprisingly, total CEA increases with family and with species diversity and observed values are the same as expected from random sampling of family lists. However, when random sampling is done from species lists, observed CEAs are generally lower than expected. In vegetation types which have undergone recent diversification—grassland, fynbos and Nama-karoo—co-occurring species are more closely related than expected, but in subtropical thicket the observed CEAs are well described by random sampling. The use of CEA has great potential for assessing the age of biotic assemblages, particularly as the dating of genus and species-level phylogenies become more accurate.

Beetle pollination of the fruit-scented cones of the South African cycad Stangeria eriopus

There has been considerable uncertainty about the importance of wind vs. insects in cycad pollination, but recent studies in several cycad genera have indicated that these are pollinated primarily, if not exclusively, by insects. Stangeria represents an isolated southern African cycad lineage previously thought to be wind-pollinated. Unlike in most other cycads, there is no evidence of cone thermogenesis in Stangeria. We found that the scent of both male and female Stangeria cones mimics that of fermented fruit, the main volatiles being esters of acetic acid, ketones, and aldehydes. We found a large variety of insect visitors on the cones, the most common ones being sap and rove beetles (Coleoptera: Nitidulidae, Staphylinidae) and fruit flies (Diptera: Drosophilidae). Of these, only sap beetles (Nitidulidae) were able to effect pollination under experimental conditions. Because sap beetles are also pollinators of Cycas and members of several ancient angiosperm families, their role in the pollination of Stangeria adds interesting details to the role this group of insects has played in the history of plant-pollinator interactions.

High-resolution satellite remote sensing: a new frontier for biodiversity exploration in Indian Himalayan forests

Satellite imagery with fine spectral and spatial resolution and high temporal resolution provides a unique opportunity to map and monitor biodiversity. The aim of this article is (i) to review the state of the use of high-resolution remote sensing for ecological studies in the Indian Himalayan Region (IHR) and (ii) to suggest further potential avenues of research in the region using this technology. It has been recognized that the recent improvements in remote sensing have enabled researchers to categorize and spatially map species and communities and to detect vegetation types based on ecological gradients and environmental drivers. Across the globe, the use of current high-resolution imagery in vegetation studies is increasing due to their improved efficiency, as fine-scale vegetation information is needed for both theoretical understanding of the processes involved and conservation towards the maintenance of ecological functions of natural ecosystems. Remote sensing is particularly useful in the IHR, where field-based mapping of forest vegetation and land cover using conventional techniques is a cost- and time-intensive effort. Mapping fine-scale patterns of tree species using high-resolution remote-sensing data has important implications for the understanding and monitoring of ecosystem function and biodiversity patterns in forests.

How do invasive species travel to and through urban environments

Globalisation has resulted in the movement of organisms outside their natural range, often with negative ecological and economic consequences. As cities are hubs of anthropogenic activities, with both highly transformed and disturbed environments, these areas are often the first point of entry for alien species. We compiled a global database of cities with more than one million inhabitants that data had on alien species occurrence. We then identified the most prominent pathways of introduction and vectors of spread of alien species in these cities. Most species were intentionally introduced to cities and were released or escaped from confinement. The majority of alien species then spread within cities through natural means (primarily unaided dispersal). Pathway prominence varied across the taxonomic groups of alien species: the most prominent pathway for plants and vertebrates was the escape pathway; for invertebrates the stowaway and contaminant pathways were most likely to facilitate introductions. For some organisms, pathway prominence varied with the geographical and climatic characteristics of the city. The characteristics of the cities also influenced the prominence of vectors of spread for alien species. Preventing the natural spread of alien species within cities, and into adjacent natural environments will be, at best, difficult. To prevent invasions, both the intentional and unintentional introduction of potentially harmful alien species to cities must be prevented. The pathways of introduction and vectors of spread identified here should be prioritised for management.

Global hotspots in the present-day distribution of ancient animal and plant lineages

The current distribution of biotic lineages that emerged in the deep time has both theoretical and practical implications, in particular for understanding the processes that have forged present-day biodiversity and informing local and regional-scale conservation efforts. To date however, there has been no examination of such patterns globally across taxa and geological time. Here we map the diversity of selected extant seed plant and tetrapod vertebrate lineages that were already in existence either in the latest Triassic or latest Cretaceous. For Triassic-age linages, we find concentrations in several regions – both tropical and temperate – parts of North America, Europe, East and South-east Asia, northern South America, and New Zealand. With Cretaceous-age lineages, high values are relatively uniformly distributed across the tropics, with peak the values along the Andes, in South-east Asia and Queensland, but also in the temperate Cape Mountains. These patterns result from a combination of factors, including land area, geographic isolation, climate stability and mass extinction survival ability. While the need to protect many of these lineages has been long recognised, a spatially-explicit approach is critical for understanding and maintaining the factors responsible for their persistence, and this will need to be taken forward across finer scales.

A global assessment of a large monocot family highlights the need for group-specific analyses of invasiveness

There are several emerging generalizations in invasion biology, but often the factors determining invasiveness are group-specific. Similar to other plant families, Araceae species (arums or aroids) with large native ranges and that have been widely introduced are more likely to become invasive. What is unique to the family is the great diversity of growth forms, some more likely to become invasive than others. We identify nine lineages in the family that have a greater tendency to invasiveness (including the duckweed lineage, as well as the genera Alocasia and Epipremnum). A precautionary approach should be taken for such clades.

Beetle assemblages of indigenous and alien decomposing fruit in subtropical Durban, South Africa

Ecological theory predicts that insect assemblages on indigenous plants will be more diverse than those on alien plants. However, this theory refers primarily to herbivores, and its applicability to decomposers is unclear. Here, we compare beetle assemblages from the fallen fruit of the two most common plants producing large fleshy fruit at our study site in Durban, South Africa: one indigenous African plant (the toad tree, Tabernaemontana ventricosa, Apocynaceae) and one invasive tropical American one (the granadilla, Passiflora edulis, Passifloraceae), at various stages of the decomposition process, thus spanning a continuum between herbivory and detritivory. Beetles found on the two plants included both alien (some categorized as pests of stored fruit) and indigenous species (including some localized endemics). We found that the mean diversity and abundance were not significantly different between the two plant species (with nine beetles from four morphospecies in the average sample) and that the beetle assemblages from the two plant species largely overlap. Statistical analyses suggested that other factors such as stage of fruit decomposition and seasonality could have greater influence on diversity and abundance than the provenance of the plant species. We conclude that insect–plant interactions in the emerging ecosystems that include indigenous and alien species in both groups are complex and that the importance of interactions between species of different provenances may have previously been underestimated.