Land snail biogeography and endemism in south-eastern Africa: Implications for the Maputaland-Pondoland-Albany biodiversity hotspot.

Invertebrates in general have long been underrepresented in studies on biodiversity, biogeography and conservation. Boundaries of biodiversity hotspots are often delimited intuitively based on floristic endemism and have seldom been empirically tested using actual species distributions, and especially invertebrates. Here we analyse the zoogeography of terrestrial malacofauna from south-eastern Africa (SEA), proposing the first mollusc-based numerical regionalisation for the area. We also discuss patterns and centres of land snail endemism, thence assessing the importance and the delimitation of the Maputaland-Pondoland-Albany (MPA) biodiversity hotspot for their conservation. An incidence matrix compiled for relatively well-collected lineages of land snails and slugs (73 taxa in twelve genera) in 40 a priori operational geographic units was subjected to (a) phenetic agglomerative hierarchical clustering using unweighted pair-group method with arithmetic means (UPGMA), (b) parsimony analysis of endemicity (PAE) and biotic element analysis (BEA). Fulfilling the primary objective of our study, the UPGMA dendrogram provided a hierarchical regionalisation and identified five centres of molluscan endemism for SEA, while the PAE confirmed six areas of endemism, also supported by the BEA. The regionalisation recovers a zoogeographic province similar to the MPA hotspot, but with a conspicuous westward extension into Knysna (towards the Cape). The MPA province, centres and areas of endemism, biotic elements as well as the spatial patterns of species richness and endemism, support the MPA hotspot, but suggest further extensions resulting in a greater MPA region of land snail endemism (also with a northward extension into sky islands-Soutpansberg and Wolkberg), similar to that noted for vertebrates. The greater MPA region provides a more robustly defined region of conservation concern, with centres of endemism serving as local conservation priorities.

Vertebrate endemism in south-eastern Africa numerically redefines a biodiversity hotspot.

We use numerical methods to explore patterns of vertebrate endemism in south-eastern Africa, refining the boundaries of the intuitively-defined Maputaland-Pondoland-Albany biodiversity hotspot, also proposing a zoogeographic regionalisation. An incidence matrix of 300 vertebrate species endemic to south-eastern Africa sensu lato in 37 operational geographic units were used in (a) phenetic cluster analysis (PCA) using the algorithm of unweighted pair-group method with arithmetic averages (phenetic approach), and (b) parsimony analysis of endemicity (PAE; parsimony approach), in order to numerically evaluate the bioregional delimitations. The analyses provide a valid biogeographical entity 37% larger than the Maputaland-Pondoland-Albany hotspot, but substantially (131%) higher in vertebrate endemicity viz. the Greater Maputaland-Pondoland-Albany (GMPA) region of vertebrate endemism. South-east Africa is recognised as a dominion in the global zoogeographical area hierarchy, with subordinate units including the GMPA province. Various spatially-based measures of endemism were mapped for vertebrate species restricted to the dominion, i.e. endemic to south-eastern Africa sensu stricto. Areas and centres of endemism detected respectively from PAE and PCA, within the south-east Africa dominion also support the refined boundary of the GMPA region of endemism, which provides a better spatial conservation priority compared to the Maputaland-Pondoland-Albany hotspot. Reptiles and amphibians are found to be the main drivers of the overall pattern of endemism, while the pattern in freshwater fish is the most distinctive. Our analyses also indicate a good congruence of the centres of endemism across different terrestrial vertebrate taxa.

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

Significant progress has been made in understanding biological invasions recently, and one of the key findings is that the determinants of naturalization and invasion success vary from group to group. Here, we explore this variation for one of the largest plant families in the world, the Araceae. This group provides an excellent opportunity for identifying determinants of invasiveness in herbaceous plants, since it is one of the families most popular with horticulturalists, with species occupying various habitats and comprising many different life forms. We first developed a checklist of 3494 species of Araceae using online databases and literature sources. We aimed to determine whether invasiveness across the introduction-naturalization-invasion continuum is associated to particular traits within the family, and whether analyses focussed on specific life forms can reveal any mechanistic correlates. Boosted regression tree models were based on species invasion statuses as the response variables, and traits associated with human use, biological characteristics and distribution as the explanatory variables. The models indicate that biological traits such as plant life form and pollinator type are consistently strong correlates of invasiveness. Additionally, large-scale correlates such as the number of native floristic regions and number of introduced regions are also influential at particular stages in the invasion continuum. We used these traits to build a phenogram showing groups defined by the similarity of characters. We identified nine groups that have a greater tendency to invasiveness (includingAlocasia, the Lemnoideae andEpipremnum). From this, we propose a list of species that are not currently invasive for which we would recommend a precautionary approach to be taken. The successful management of plant invasions will depend on understanding such context-dependent effects across taxonomic groups, and across the different stages of the invasion process.

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 lineages, 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.

How do alien plants fit in the space-phylogeny matrix?

Recent advances in the field of plant community phylogenetics and invasion phylogenetics are mostly based on plot-level data, which do not take into consideration the spatial arrangement of individual plants within the plot. Here we use within-plot plant coordinates to investigate the link between the physical distance separating plants, and their phylogenetic relatedness. We look at two vegetation types (forest and grassland, similar in species richness and in the proportion of alien invasive plants) in subtropical coastal KwaZulu-Natal, South Africa. The relationship between phylogenetic distance and physical distance is weak in grassland (characterised by higher plant densities and low phylogenetic diversity), and varies substantially in forest vegetation (variable plant density, higher phylogenetic diversity). There is no significant relationship between the proportion of alien plants in the plots and the strength of the physical-phylogenetic distance relationship, suggesting that alien plants are well integrated in the local spatial-phylogenetic landscape.

K-Pg events facilitated lineage transitions between terrestrial and aquatic ecosystems.

We use dated phylogenetic trees for tetrapod vertebrates to identify lineages that shifted between terrestrial and aquatic ecosystems in terms of feeding or development, and to assess the timing of such events. Both stem and crown lineage ages indicate a peak in transition events in correspondence with the K-Pg mass extinction. This meets the prediction that changes in competitive pressure and resource availability following mass extinction events should facilitate such transitions.

Low persistence of a monocarpic invasive plant in historical sites biases our perception of its actual distribution.

AIM: As accurate and up-to-date distribution data for plant species are rarely available, cumulative records over long periods of time are frequently used for mapping distributions, without taking into account that species do not persist in their historical localities forever. However, persistence is highly relevant in changing modern landscapes, especially for invasive species that dynamically spread in unstable human-made habitats. We studied how an invasive species, Heracleum mantegazzianum, persists at sites once colonized and how its ability to persist affects its distribution. LOCATION: The Czech Republic. METHODS: We visited 521 localities of H. mantegazzianum occurrence reported in the literature and herbaria to determine whether the species still occurs at these sites. By using G-tests and classification trees, we explored the roles of various factors affecting its persistence at a site. RESULTS: Of the total number of 521 historical sites at which the species has occurred since the end of the 19th century, it persists at only 124 (23.8%). The persistence rate differs with respect to habitat type and is highest in meadows and forest margins. Analysis using classification trees indicated that the factors that best explain persistence are: type of habitat (with meadow and forest margins over-represented); urbanity (with a higher persistence outside urban areas); proximity to the place of the species' introduction into the country; metapopulation connectivity; and distance to the nearest neighbouring population. MAIN CONCLUSIONS: The use of cumulative historical records as a measure of species distribution, which is common in invasion literature, can seriously overestimate the actual distribution of alien plant species with low persistence. In the case of alien species such as H. mantegazzanium, which is non-clonal and reproduces only by seed, estimates of distribution and spread based on historical data are informative about potentially suitable habitat but may be unreliable as indicators of current occurrence and invasion dynamics.

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.

Explaining the uniqueness of the Cape flora: incorporating geomorphic evolution as a factor for explaining its diversification.

The plant diversity of the Cape Floristic Region is regarded as being exceptional in an ecological and evolutionary context. The region supports about double the number of species predicted by models based on water-energy variables for regional floras globally. However, contemporary diversity patterns are profoundly influenced by evolutionary processes contingent upon idiosyncrasies of history and geography. The relatively recent appearance of dated molecular phylogenies, and their optimization in relation to habitat and geography, has provided hitherto unsurpassed opportunities to generate knowledge about the evolution of the Cape flora. Almost all studies invoke climatic deterioration during the Mio-Pliocene as the major trigger of radiations and subsequent speciation of Cape clades. While some do show the importance of edaphic heterogeneity for clade radiation, the evolution of this heterogeneity is not considered. Here, we review the literature on the late Cenozoic geomorphic evolution of the Cape in order to assess the extent to which the changing nature of scenery and soils could act as a stimulus for plant diversification. Despite dating uncertainties associated with both the phylogenetic and geomorphic data, it appears that moderate uplift in the early and late Miocene, which significantly increased the topo-edaphic heterogeneity of the Cape was an important driver of plant diversification. In particular, the massive increase in heterogeneity after the late Miocene event probably acted in synergy with rapid climatic deterioration, to produce the extraordinarily rapid diversification recorded for some Cape clades at that time. A comparison of the plant diversity and palaeoenvironmetal patterns of mediterranean-climate regions provide insights regarding the "remarkable environmental conditions" of the Cape that have generated the high diversification and low extinction rates necessary to produce such a rich flora. These conditions are a gradual increase in topo-edaphic heterogeneity and relative climatic stability during the late Cenozoic.

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.

Preserving the evolutionary potential of floras in biodiversity hotspots.

One of the biggest challenges for conservation biology is to provide conservation planners with ways to prioritize effort. Much attention has been focused on biodiversity hotspots. However, the conservation of evolutionary process is now also acknowledged as a priority in the face of global change. Phylogenetic diversity (PD) is a biodiversity index that measures the length of evolutionary pathways that connect a given set of taxa. PD therefore identifies sets of taxa that maximize the accumulation of 'feature diversity'. Recent studies, however, concluded that taxon richness is a good surrogate for PD. Here we show taxon richness to be decoupled from PD, using a biome-wide phylogenetic analysis of the flora of an undisputed biodiversity hotspot--the Cape of South Africa. We demonstrate that this decoupling has real-world importance for conservation planning. Finally, using a database of medicinal and economic plant use, we demonstrate that PD protection is the best strategy for preserving feature diversity in the Cape. We should be able to use PD to identify those key regions that maximize future options, both for the continuing evolution of life on Earth and for the benefit of society.

Latitudinal and longitudinal barriers in global biogeography.

Due to changes in climate and continental arrangement, plant and animal assemblages faced different dispersal barriers at different moments in Earth's history. It is generally accepted that groups which diversified during times of Gondwanan-Laurasian separation show different distribution patterns from those of more recent origin. Here I present principal component-derived maps for two globally distributed groups, with ca 1000 species each. Gymnosperm assemblages perfectly illustrate the existence of southern and northern components, corresponding to the Gondwanan and Laurasian temperate floras at the time when angiosperms started becoming dominant in the tropics, thus imposing a latitudinal barrier. Bat (chiropteran) assemblages indicate that the major biogeographical barrier in their Cenozoic dispersal was the longitudinal separation between the Old and New World.

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.

How much evolutionary history in a 10 x 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.