Amphibian Diversity in East African Biodiversity Hotspots: Altitudinal and latitudinal Patterns

The Eastern Arc mountain chain and adjoining coastal forests of Tanzania and Kenya have been listed as world biodiversity hotspots. We report on an ongoing attempt to estimate amphibian diversity on the three best studied mountains of the Eastern Arc, the East Usambara, Uluguru and Udzungwa mountains of Tanzania, complemented by an estimate of diversity on the adjoining coastal lowland. This proves to be a complex task, which introduces a note of caution into evaluating global biodiversity estimates. Most amphibian species in eastern Tanzania occur on the coastal lowlands and are widely distributed, extending at least north or south of Tanzania and, to a variable extent, westwards to the elevated interior. Diversity patterns along the length of the lowlands are complex, with the presence of a Sahelian element in the extreme north. On the three Eastern Arc mountains studied, species turnover associated with rising altitude is greater than turnover associated with latitudinal distance between the mountain blocks, leading to greater altitudinal than latitudinal diversity in this equatorial region. A long-standing divergence is indicated between montane and lowland endemics. Although forest-associated species are not the largest contributor to the eastern Tanzanian total species diversity (some 48%), the uniqueness of these species both in lowland and montane forests, combined with their evident vulnerability to disturbance, makes them a subject for particular conservation concern, and justifies hotspot status for both montane and lowland forests.     

Vegetation of Kilimanjaro: hidden endemics and missing bamboo

Kilimanjaro has a large variety of forest types over an altitudinal range of 3000 m containing over 1200 vascular plant species. Montane Ocotea forests occur on the wet southern slope. Cassipourea and Juniperus forests grow on the dry northern slope. Subalpine Erica forests at 4100 m represent the highest elevation cloud forests in Africa. In contrast to this enormous biodiversity, the degree of endemism is low. However, forest relicts in the deepest valleys of the cultivated lower areas suggest that a rich forest flora inhabited Mt Kilimanjaro in the past, with restricted‐range species otherwise only known from the Eastern Arc mountains. The low degree of endemism on Kilimanjaro may result from destruction of lower altitude forest rather than the relatively young age of the mountain. Another feature of the forests of Kilimanjaro is the absence of a bamboo zone, which occurs on all other tall mountains in East Africa with a similarly high rainfall. Sinarundinaria alpina stands are favoured by elephants and buffaloes. On Kilimanjaro these megaherbivores occur on the northern slopes, where it is too dry for a large bamboo zone to develop. They are excluded from the wet southern slope forests by topography and humans, who have cultivated the foothills for at least 2000 years. This interplay of biotic and abiotic factors could explain not only the lack of a bamboo zone on Kilimanjaro but also offers possible explanations for the patterns of diversity and endemism. Kilimanjaro's forests can therefore serve as a striking example of the large and long‐lasting influence of both animals and humans on the African landscape.     

Evolutionary and demographic processes shaping geographic patterns of genetic diversity in a keystone species,the African forest elephant (Loxodonta cyclotis)

The past processes that have shaped geographic patterns of genetic diversity may be difficult to infer from current patterns. However, in species with sex differences in dispersal, differing phylogeographic patterns between mitochondrial (mt) and nuclear (nu) DNA may provide contrasting insights into past events. Forest elephants (Loxodonta cyclotis) were impacted by climate and habitat change during the Pleistocene, which likely shaped phylogeographic patterns in mitochondrial (mt) DNA that have persisted due to limited female dispersal. By contrast, the nuclear (nu) DNA phylogeography of forest elephants in Central Africa has not been determined. We therefore examined the population structure of Central African forest elephants by genotyping 94 individuals from six localities at 21 microsatellite loci. Between forest elephants in western and eastern Congolian forests, there was only modest genetic differentiation, a pattern highly discordant with that of mtDNA. Nuclear genetic patterns are consistent with isolation by distance. Alternatively, male‐mediated gene flow may have reduced the previous regional differentiation in Central Africa suggested by mtDNA patterns, which likely reflect forest fragmentation during the Pleistocene. In species like elephants, male‐mediated gene flow erases the nuclear genetic signatures of past climate and habitat changes, but these continue to persist as patterns in mtDNA because females do not disperse. Conservation implications of these results are discussed.     

Diversification in a biodiversity hot spot: landscape correlates of phylogeographic patterns in the African spotted reed frog

The Eastern Afromontane Biodiversity Hotspot is known for microendemism and exceptional population genetic structure. The region's landscape heterogeneity is thought to limit gene flow between fragmented populations and create opportunities for regional adaptation, but the processes involved are poorly understood. Using a combination of phylogeographic analyses and circuit theory, I investigate how characteristics of landscape heterogeneity including regional distributions of slope, rivers and streams, habitat and hydrological basins (drainages) impact genetic distance among populations of the endemic spotted reed frog (Hyperolius substriatus), identifying corridors of connectivity as well as barriers to dispersal. Results show that genetic distance among populations is most strongly correlated to regional and local hydrologic structure and the distribution of suitable habitat corridors, not isolation by distance. Contrary to expectations, phylogeographic structure is not coincident with the two montane systems, but instead corresponds to the split between the region's two major hydrological basins (Zambezi and East Central Coastal). This results in a paraphyletic relationship for the Malawian Highlands populations with respect to the Eastern Arc Mountains and implies that the northern Malawian Highlands are the diversity centre for H. substriatus. Although the Malawian Highlands collectively hold the greatest genetic diversity, individual populations have lower diversity than their Eastern Arc counterparts, with an overall pattern of decreasing population diversity from north to south. Through the study of intraspecific differentiation across a mosaic of ecosystem and geographic heterogeneity, we gain insight into the processes of diversification and a broader understanding of the role of landscape in evolution.     

Effects of fire on understorey birds in Kimboza Forest Reserve in the eastern foothills of the Uluguru Mountains,Tanzania

Fire is one of the main threats facing the long‐term survival of the forests in the Eastern Arc Mountains. Yet, our understanding of how it affects fauna, particularly birds, is still poor. A fire that originated on surrounding farmland burned approximately half of Kimboza Forest Reserve between 13 and 15 October 2010. To better understand how birds respond to fire, a short‐term study of understorey bird diversity and abundance in this forest reserve was conducted by comparing burned and unburned sites twenty months post‐fire. Capture rates were significantly higher at the unburned site compared to the burned site. Bird species diversity was also higher at the unburned site than at the burned site. Despite the brevity of the study, the results suggest that fire has negative effects on forest avifauna and forest fires need to be prevented at Kimboza Forest Reserve as they affect the distribution and diversity of understorey birds.     

Impacts of Restored Patch Density and Distance from Natural Forests on Colonization Success

Abstract The reduction and fragmentation of forest habitats is expected to have profound effects on plant species diversity as a consequence of the decreased area and increased isolation of the remnant patches. To stop the ongoing process of forest fragmentation, much attention has been given recently to the restoration of forest habitat. The present study investigates restoration possibilities of recently established patches with respect to their geographical isolation. Because seed dispersal events over 100 m are considered to be of long distance, a threshold value of 100 m between recent and old woodland was chosen to define isolation. Total species richness, individual patch species richness, frequency distributions in species occurrences, and patch occupancy patterns of individual species were significantly different among isolated and nonisolated stands. In the short term no high species richness is to be expected in isolated stands. Establishing new forests adjacent to existing woodland ensures higher survival probabilities of existing populations. In the long term, however, the importance of long‐distance seed dispersal should not be underestimated because most species showed occasional long‐distance seed dispersal. A clear distinction should be made between populations colonizing adjacent patches and patches isolated from old woodland. The colonization of isolated stands may have important effects on the dynamics and diversity of forest networks, and more attention should be directed toward the genetic traits and viability of founding populations in isolated stands.     

Seasonal variation in diversity and abundance of understorey birds in Bunduki Forest Reserve,Tanzania: evaluating the conservation value of a plantation forest

Plantation forests generally support lower bird diversity than natural forests. However, in some instances the plantations have been found to provide suitable habitat for a number of bird species. In the Eastern Arc Mountains, there is limited knowledge how understorey birds, some of which make seasonal altitudinal movements, use plantations. Using mist netting we assessed seasonal use of the plantation forest by the understorey bird community in Bunduki Forest Reserve in the Uluguru Mountains. Species diversity and capture rates were significantly higher during the cold season than during the hot season possibly due to seasonal altitudinal migration by some species. The use of plantations by those species that make seasonal altitudinal movements shows that plantation forests can enhance indigenous biodiversity by enabling connectivity between two or more natural forest patches. Our findings suggest that in a situation where there is no natural forest, an exotic plantation with suitable indigenous understorey cover can help in protection of birds, including endemic and near-endemic species.     

Climatic niche and neutral genetic diversity of the six Iberian pine species: a retrospective and prospective view

Quaternary climatic fluctuations have left contrasting historical footprints on the neutral genetic diversity patterns of existing populations of different tree species. We should expect the demography, and consequently the neutral genetic structure, of taxa less tolerant to particular climatic extremes to be more sensitive to long‐term climate fluctuations. We explore this hypothesis here by sampling all six pine species found in the Iberian Peninsula (2464 individuals, 105 populations), using a common set of chloroplast microsatellite markers, and by looking at the association between neutral genetic diversity and species‐specific climatic requirements. We found large variation in neutral genetic diversity and structure among Iberian pines, with cold‐enduring mountain species (Pinus uncinata, P. sylvestris and P. nigra) showing substantially greater diversity than thermophilous taxa (P. pinea and P. halepensis). Within species, we observed a significant positive correlation between population genetic diversity and summer precipitation for some of the mountain pines. The observed pattern is consistent with the hypotheses that: (i) more thermophilous species have been subjected to stronger demographic fluctuations in the past, as a consequence of their maladaptation to recurrent glacial cold stages; and (ii) altitudinal migrations have allowed the maintenance of large effective population sizes and genetic variation in cold‐tolerant species, especially in more humid regions. In the light of these results and hypotheses, we discuss some potential genetic consequences of impending climate change.     

Ancient forest fragmentation or recent radiation? Testing refugial speciation models in chameleons within an African biodiversity hotspot

Aim East Africa is one of the most biologically diverse regions, especially in terms of endemism and species richness. Hypotheses put forward to explain this high diversity invoke a role for forest refugia through: (1) accumulation of new species due to radiation within refugial habitats, or (2) retention of older palaeoendemic species in stable refugia. We tested these alternative hypotheses using data for a diverse genus of East African forest chameleons, Kinyongia. Location East Africa. Methods We constructed a dated phylogeny for Kinyongia using one nuclear and two mitochondrial markers. We identified areas of high phylogenetic diversity (PD) and evolutionary diversity (ED), and mapped ancestral areas to ascertain whether lineage diversification could best be explained by vicariance or dispersal. Results Vicariance best explains the present biogeographic patterns, with divergence between three major Kinyongia clades (Albertine Rift, southern Eastern Arc, northern Eastern Arc) in the early Miocene/Oligocene (> 20 Ma). Lineage diversification within these clades pre‐dates the Pliocene (> 6 Ma). These dates are much older than the Plio‐Pleistocene climatic shifts associated with cladogenesis in other East African taxa (e.g. birds), and instead point to a scenario whereby palaeoendemics are retained in refugia, rather than more recent radiations within refugia. Estimates of PD show that diversity was highest in the Uluguru, Nguru and East Usambara Mountains and several lineages (from Mount Kenya, South Pare and the Uluguru Mountains) stand out as being evolutionarily distinct as a result of isolation in forest refugia. PD was lower than expected by chance, suggesting that the phylogenetic signal is influenced by an unusually low number of extant lineages with long branch lengths, which is probably due to the retention of palaeoendemic lineages. Main conclusions The biogeographic patterns associated with Kinyongia are the result of long evolutionary histories in isolation. The phylogeny is dominated by ancient lineages whose origins date back to the early Miocene/Oligocene as a result of continental wide forest fragmentation and contraction due to long term climatic changes in Africa. The maintenance of palaeoendemic lineages in refugia has contributed substantially to the remarkably high biodiversity of East Africa.     

Population signatures of large-scale,long-term disjunction and small-scale,short-term habitat fragmentation in an Afromontane forest bird

The Eastern Afromontane cloud forests occur as geographically distinct mountain exclaves. The conditions of these forests range from large to small and from fairly intact to strongly degraded. For this study, we sampled individuals of the forest bird species, the Montane White-eye Zosterops poliogaster from 16 sites and four mountain archipelagos. We analysed 12 polymorphic microsatellites and three phenotypic traits, and calculated Species Distribution Models (SDMs) to project past distributions and predict potential future range shifts under a scenario of climate warming. We found well-supported genetic and morphologic clusters corresponding to the mountain ranges where populations were sampled, with 43% of all alleles being restricted to single mountains. Our data suggest that large-scale and long-term geographic isolation on mountain islands caused genetically and morphologically distinct population clusters in Z. poliogaster. However, major genetic and biometric splits were not correlated to the geographic distances among populations. This heterogeneous pattern can be explained by past climatic shifts, as highlighted by our SDM projections. Anthropogenically fragmented populations showed lower genetic diversity and a lower mean body mass, possibly in response to suboptimal habitat conditions. On the basis of these findings and the results from our SDM analysis we predict further loss of genotypic and phenotypic uniqueness in the wake of climate change, due to the contraction of the species'' climatic niche and subsequent decline in population size.     

Seasonal use of remnant forest fragments by understorey forest birds in the Uluguru Mountains,Tanzania: a conservation priority

Forest fragmentation can lead to extinctions of some species at local levels and is eroding bird diversity at an increasing rate. While there is information on the distribution of forest bird species in most of the Eastern Arc Mountain forests, some forests, particularly the smaller fragments, have not been adequately surveyed. Using mist netting we surveyed avifauna in some of the poorly known forests (12.5–25 ha) located 320–1 300 m above sea level in the Uluguru Mountains in order to address their conservation importance. Proportions of seasonal altitudinal migrants were significantly higher in these lower-altitude forests during the cold season than the hot season. The results suggest that these forests support bird species of conservation concern, most of which are forest dependent and some of which make seasonal movements between high-altitude montane forests and lowland/ foothill forests. These forests are important cold-season habitat of altitudinal migrants and further fragmentation should be halted as a matter of regional and global priority.     

Biogeographic patterns of the East African coastal forest vertebrate fauna

The archipelago-like coastal forest of East Africa is one of the highest priority ecosystems for biodiversity conservation worldwide. Here we investigate patterns of species richness and biogeographic distribution among birds, mammals and reptiles of these forests, using distribution data obtained from recently published reviews and information collated by the WWF Eastern Africa Coastal Forest Ecoregion Programme. Birds and mammals species were divided into forest specialists and generalists, and forest specialist reptiles into ‘coastal’ and ‘forest’ endemics. The species richness of birds and generalist mammals increased with area, and is probably a result of area-dependent extinction. Only in birds, however, species richness increased with decreasing isolation, suggesting possible isolation-dependent colonization. Forest diversity, associated to altitudinal range, is important for specialist birds and mammals, whose species richness increased with wider altitudinal range. The number of relict coastal endemic and forest endemic reptiles was higher in forests with wider altitudinal ranges and on relatively higher altitude, respectively. Such forests have probably provided a suitable (and perhaps stable) environment for these species through time, thus increasing their persistence. Parsimony analysis of distributions (PAD) and cluster analyses showed geographical distance and general ecological similarity among forests as a determinant factor in bird distribution patterns, with compositional similarity decreasing with increasing inter-forest distance. Compositional similarity patterns of mammals among the forests did not show a strong geographical correspondence or a significant correlation with inter-forest distance, and those of reptiles were not resolved, with very low similarity levels among forest faunas. Our results suggest that the relative importance (and causal relationship) of forest attributes affecting the distribution of the East African coastal forest vertebrate fauna varies depending on life history traits such as dispersal ability and forest specialization. The groupings in PAD are partly congruent with some of the previous classifications of areas of endemism for this region, supporting the ‘naturalness’ of these regions.     

Landscape genetics indicate recently increased habitat fragmentation in African forest‐associated chafers

Today, indigenous forests cover less than 0.6% of South Africa's land surface and are highly fragmented. Most forest relicts are very small and typically occur in fire‐protected gorges along the eastern Great Escarpment. Yet, they hold a unique and valuable fauna with high endemism and ancient phylogenetic lineages, fostered by long‐term climatic stability and complex microclimates. Despite numerous studies on southern African vegetation cover, the current state of knowledge about the natural extension of indigenous forests is rather fragmentary. We use an integrated approach of population‐level phylogeography and climatic niche modeling of forest‐associated chafer species to assess connectivity and extent of forest habitats since the last glacial maximum. Current and past species distribution models ascertained potential fluctuations of forest distribution and supported a much wider potential current extension of forests based on climatic data. Considerable genetic admixture of mitochondrial and nuclear DNA among many populations and an increase in mean population mutation rate in Extended Bayesian Skyline Plots of all species indicated more extended or better connected forests in the recent past (<5 kya). Genetic isolation of certain populations, as revealed by population differentiation statistics (), as well as landscape connectivity statistics and habitat succession scenarios suggests considerable loss of habitat connectivity. As major anthropogenic influence is likely, conservational actions need to be considered.     

Large-scale phylogeography of the disjunct Neotropical tree species Schizolobium parahyba (Fabaceae-Caesalpinioideae)

Neotropical rainforests exhibit high levels of endemism and diversity. Although the evolutionary genetics of plant diversification has garnered increased interest, phylogeographic studies of widely distributed species remain scarce. Here we describe chloroplast and nuclear variation patterns in Schizolobium parahyba (Fabaceae), a widespread tree in Neotropical rainforests that harbor two varieties with a disjunct distribution. Chloroplast and nuclear sequence analyses yielded 21 and 4 haplotypes, respectively. Two genetic diversity centers that correlate with the two known varieties were identified: the Southeastern Atlantic forest and the Amazonian basin. In contrast, the populations from southern and northeastern Atlantic forests and Andean-Central American forests exhibited low levels of genetic diversity and divergent haplotypes, likely related to historical processes that impact the flora and fauna in these regions, such as a founder's effect after dispersion and demographic expansion. Phylogeographic and demographic patterns suggest that episodes of genetic isolation and dispersal events have shaped the evolutionary history for this species, and different patterns have guided the evolution of S. parahyba. Moreover, the results of this study suggest that the dry corridor formed by Cerrado and Caatinga ecoregions and the Andean uplift acted as barriers to this species' gene flow, a picture that may be generalized to most of the plant biodiversity tropical woodlands and forests. These results also reinforce the importance of evaluating multiple genetic markers for a more comprehensive understanding of population structure and history. Our results provide insight into the conservation efforts and ongoing work on the genetics of population divergence and speciation in these Neotropical rainforests.     

Oceanographic features and limited dispersal shape the population genetic structure of the vase sponge Ircinia campana in the Greater Caribbean

Understanding population genetic structure can help us to infer dispersal patterns, predict population resilience and design effective management strategies. For sessile species with limited dispersal, this is especially pertinent because genetic diversity and connectivity are key aspects of their resilience to environmental stressors. Here, we describe the population structure of Ircinia campana, a common Caribbean sponge subject to mass mortalities and disease. Microsatellites were used to genotype 440 individuals from 19 sites throughout the Greater Caribbean. We found strong genetic structure across the region, and significant isolation by distance across the Lesser Antilles, highlighting the influence of limited larval dispersal. We also observed spatial genetic structure patterns congruent with oceanography. This includes evidence of connectivity between sponges in the Florida Keys and the southeast coast of the United States (>700 km away) where the oceanographic environment is dominated by the strong Florida Current. Conversely, the population in southern Belize was strongly differentiated from all other sites, consistent with the presence of dispersal-limiting oceanographic features, including the Gulf of Honduras gyre. At smaller spatial scales (<100 km), sites showed heterogeneous patterns of low-level but significant genetic differentiation (chaotic genetic patchiness), indicative of temporal variability in recruitment or local selective pressures. Genetic diversity was similar across sites, but there was evidence of a genetic bottleneck at one site in Florida where past mass mortalities have occurred. These findings underscore the relationship between regional oceanography and weak larval dispersal in explaining population genetic patterns, and could inform conservation management of the species.Subject terms: Genetic variation, Ecology     

Genetic structure of montane isolates of Pinus sylvestris L. in a Mediterranean refugial area

Aim This work investigates the population genetic effects of periodic altitudinal migrations and interstadial fragmentation episodes in long‐term Scots pine (Pinus sylvestris L.) populations at a regional scale. Location The study focuses on Scots pine populations in the northern Meseta and peripheral mountain chains, central and north‐western Iberian Peninsula. The ample macrofossil record in the area shows that this 60,000‐km² region represent a glacial refugium for Scots pine. The species occupied large areas on the Meseta plains during glacial cold stages, but it has periodically sheltered at high elevation in the surrounding mountain chains during warm episodes, conforming to a fragmented pattern similar to its present‐day distribution. Methods We perform a fine‐scale chloroplast microsatellite (cpSSR) survey to assess the genetic structure of 13 montane Scots pine isolates in the northern Meseta (total N = 322 individuals). Using a hierarchical analysis of molecular variance (amova ), we test the hypothesis of genetic isolation among disjunct mountain areas. We use a standard coalescence model to estimate genealogical relationship among populations, investigating the potential role of the regional relief as a factor influencing historic gene exchange among Scots pine populations. Results Population haplotypic diversity was high among Scots pine populations (H_e = 0.978), greater than values reported for other more thermophilic pine species in the Iberian Peninsula. The amova revealed low (but significant) differentiation among populations (Φ_ST = 0.031, P = 0.010), showed that the disjoint montane distribution could not account for the genetic divergence among areas (Φ_CT = 0.012, P = 0.253), and that there was non‐trivial subdivision among populations within the same mountain region (Φ_SC = 0.021, P = 0.012). The genealogical relationships among populations showed that Scots pine isolates growing on disjoint mountain blocks, but on slopes flowing to the same basin, were genetically closer than populations growing on different slopes of the same mountain chain, flowing to different basins. Main conclusions The observed genetic structure for Scots pine is consistent with its population history, inferred from the palaeobotanical record, with vertical migrations throughout climatic pulses and with the drainage basins and large long‐term population sizes connecting different mountain blocks during the cooler glacial periods. Overall, the results suggest that, despite periodic interstadial fragmentation episodes, Scots pine biology provides for the long‐term maintenance of high within‐population and low among‐population genetic diversity at neutral genetic markers.     

Remnants fragments preserve genetic diversity of the old forest lichen <Emphasis Type="Italic">Lobaria pulmonaria</Emphasis> in a fragmented Mediterranean mountain forest

Fragmentation represents a serious threat to biodiversity worldwide, however its effects on epiphytic organisms is still poorly understood. We study the effect of habitat fragmentation on the genetic population structure and diversity of the red-listed epiphytic lichen, Lobaria pulmonaria, in a Mediterranean forest landscape. We tested the relative importance of forest patch quality, matrix surrounding fragments and connectivity on the genetic variation within populations and the differentiation among them. A total of 855 thalli were sampled in 44 plots (400 m²) of 31 suitable forest fragments (beeches and oaks), in the Sierra de Ayllón in central Spain. Variables related to landscape attributes of the remnant forest patches such as size and connectivity and also the nature of the matrix or tree species had no significant effects on the genetic diversity of L. pulmonaria. Values of genetic diversity (Nei’s) were only affected by habitat quality estimated as the age patches. Most of the variation (76%) in all populations was observed at the smallest sampled unit (plots). Using multiple regression analysis, we found that habitat quality is more important in explaining the genetic structure of the L. pulmonaria populations than spatial distance. The relatively high level of genetic diversity of the species in old forest patches regardless of patch size indicates that habitat quality in a highly structured forest stand determines the population size and distribution pattern of this species and its associated lichen community. Thus, conservation programmes of Mediterranean mountain forests have to prioritize area and habitat quality of old forest patches.     

Groupings of life‐history traits are associated with distribution of forest plant species in a fragmented landscape

Questions: 1. Do relationships among forest plant traits correspond to dispersability‐persistence trade‐offs or other inter‐trait correlations found in the literature? 2. Do species groups delineated by trait similarity, differ in occurrence in ancient vs. new forests or isolated vs more continuous forest patches? 3. Are these patterns consistent for different forest types? Location: Central Belgium, near Leuven. Methods: We investigate the distributions of a large set of plant traits and combinations among all forest species occurring in patches with varying forest continuity and isolation. Through calculation of Gower's similarity index and subsequent clustering,‘emergent’ species groups are delineated. Then, the relative occurrence of these different groups in forest patches of different age and size, sustaining different forest types (alluvial vs. Quercion), and having different isolation status is compared through multivariate GLM analysis. Results: Correlations among several life history traits point towards trade‐offs of dispersability and fecundity vs. longevity. We distinguished three species groups: 1= mainly shrubs or climbers with fleshy or wind dispersed fruits and high dispersal potential; 2 = dominated by small, mainly vegetatively reproducing herbs; 3 = with spring flowering herbs with large seeds and mainly unassisted dispersal. Relative occurrence of these groups was significantly affected by forest age, area, isolation and forest type. Separate analyses for alluvial and Quercion forests indicated that the relative importance of these factors may differ, depending on forest type and species group. Both forest continuity and isolation are important in restricting the relative occurrence of forest species in alluvial forests, whatever their group membership. In Quercion forests forest patch area was the primary determinant of relative occurrence of species groups. Conclusions: It is very important to preserve the actual forest area including the spatial setting and the dispersal infrastructure within the landscape. Next, forest connectivity may be restored, but it is inherently a long process.     

The DNA history of a lonely oak: Quercus humboldtii phylogeography in the Colombian Andes

The climatic and geological changes that occurred during the Quaternary, particularly the fluctuations during the glacial and interglacial periods of the Pleistocene, shaped the population demography and geographic distribution of many species. These processes have been studied in several groups of organisms in the Northern Hemisphere, but their influence on the evolution of Neotropical montane species and ecosystems remains unclear. This study contributes to the understanding of the effect of climatic fluctuations during the late Pleistocene on the evolution of Andean mountain forests. First, we describe the nuclear and plastidic DNA patterns of genetic diversity, structure, historical demography, and landscape connectivity of Quercus humboldtii, which is a typical species in northern Andean montane forests. Then, these patterns were compared with the palynological and evolutionary hypotheses postulated for montane forests of the Colombian Andes under climatic fluctuation scenarios during the Quaternary. Our results indicated that populations of Q. humboldtii have high genetic diversity and a lack of genetic structure and that they have experienced a historical increase in connectivity from the last glacial maximum (LGM) to the present. Furthermore, our results showed a dramatic reduction in the effective population size followed by an expansion before the LGM, which is consistent with the results found by palynological studies, suggesting a change in dominance in Andean forests that may be related to ecological factors rather than climate change.     

Changing places: how the results of new field work in the Rubeho Mountains influence conservation priorities in the Eastern Arc Mountains of Tanzania

The Rubeho Mountains are a poorly studied mountain block within the Eastern Arc Mountain range of Tanzania and Kenya. We present the results of field surveys for vertebrates undertaken during the period February 2000 to December 2002. One hundred and twelve man‐days of surveys recorded 35 mammal, 107 bird, ten reptile and nine amphibian species, including eleven species endemic and seven near‐endemic to the Eastern Arc, with one species new to science. Of these, nine species are regarded as threatened with extinction. The new survey data significantly elevate the biological importance of the Rubehos within the Eastern Arc range. Further analyses highlight how the overall biological ranking of the Eastern Arc mountain blocks is correlated with survey effort. The majority of the forest habitat on the Rubehos is contained in three national (Central Government) Forest Reserves (Mang'alisa, Mafwomero and Ukwiva). Our surveys recorded high levels of disturbance to the forest habitat in all three reserves and we draw attention to the need for additional conservation investment in this area.