Dendrochronological investigation of the high Andean tree species <Emphasis Type="Italic">Polylepis besseri</Emphasis> and implications for management and conservation

High-altitude Polylepis besseri woodlands in Bolivia are under increasing threat from human use and disturbance. Currently, there is no information regarding P. besseri growth rates, age structures or the relationship between environmental variables and growth. Such information would be useful for effective management and conservation of the remaining woodlands. We used standard dendrochronological techniques to determine the age and radial growth rates for 23 trees from two Polylepis besseri populations in Sacha Loma (mountains Uypa and Chutu Senega), and investigated the relationship between climate and radial growth. Wood samples exhibited semicircular porosity and visible tree-ring boundaries. The sample trees were young (mean age 40 years, max age 63 years) and growing slowly (<1 mm/year). Trees at Chutu Senega were older and growing more slowly than those at Uypa. The strong linearity of cumulated radial increments suggest that P. besseri may maintain consistent growth rates beyond 60 years. Our results indicate that radial growth is limited by the accumulation of reserves the year before ring formation, and that a warm period before the growing season (humid period) can increase P. besseri’s growth in the Bolivian-Tucuman biogeographic Province. It seems that local factors are more important than regional factors in these high Andean woodlands. This study improves our understanding of the biology of Polylepis and demonstrates the usefulness of dendrochronology for investigating the biotic, abiotic and anthropogenic effects on woodlands in areas lacking long term historical data.     

Genetic footprints of habitat fragmentation in the extant populations of Sinojackia (Styracaceae): implications for conservation

Sinojackia, a member of the family Styracaceae, is an endangered genus endemic to China. The number of populations and population size of Sinojackia have decreased sharply because of habitat fragmentation and destruction. We studied the genetic diversity of extant populations in two different cohorts (adult and seedling) using eight microsatellite markers to investigate the genetic footprints of habitat fragmentation in four recognized Sinojackia spp. and to develop appropriate conservation measures. Data on intrapopulational genetic diversity suggest that Sinojackia populations have maintained relatively high levels of genetic diversity and low levels of genetic differentiation despite severe fragmentation. The high genetic diversity may be explained by the outcrossing mating system and high longevity of Sinojackia spp. The amount of genetic variation is not associated with population size, which was also supported by bottleneck analysis. In the species studied, there was no significant difference in the genetic diversity between the two cohorts analysed. However, inbreeding increased from adult trees to seedling populations, suggesting that the higher proportion of biparental inbreeding in the recent generations of seedlings is the result of restricted current genetic flow caused by habitat fragmentation. Average seed set per population was not significantly correlated with either population size or genetic diversity. Conservation management should aim to monitor inbreeding and outbreeding depression carefully to ensure the in situ and ex situ conservation of Sinojackia spp. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ?? , ??–??.     

Polylepis woodland dynamics during the last 20,000 years

Aim

To determine the palaeoecological influences of climate change and human land use on the spatial distribution patterns of Polylepis woodlands in the Andes.

Location

Tropical Andes above 2,900 m between 2°S and 18°S of latitude.

Methods

Pollen and charcoal data were gathered from 13 Andean lake sediment records and were rescaled by the maximum value in each site. The rescaled pollen data were used to estimate a mean abundance and coefficient of variation to show woodland expansions/contractions and woodland fragmentation over the last 20,000 years. The rescaled charcoal was displayed as a 200‐year moving median using 500‐year bins to infer the influence of fire on woodland dynamics at landscape scale. Pollen and charcoal were compared with speleothem, clastic flux and archaeological data to assess the influence of moisture balance, glacial activity and human impact on the spatial distribution of Polylepis woodlands.

Results

Woodland expansion and fire were correlated with precipitation changes and glacier dynamics from c. 20 to 6 kcal bp (thousands of calibrated years before present). Charcoal abundances between 20 and 12 kcal bp were less common than from 12 kcal bp to modern. However, human‐induced fires were unlikely to be the main cause of a woodland decline centred at 11 kcal bp , as woodlands recovered from 10.5 to 9.5 kcal bp (about twofold increase). Charcoal peaks analogous to those that induced the woodland decline at 11 kcal bp were commonplace post‐9.5 kcal bp but did not trigger an equivalent woodland contraction. An increase in the coefficient of variation after c. 5.5 kcal bp suggests enhanced fragmentation and coincided with the shift from logistic to exponential growth of human populations. Over the last 1,000 years, Polylepis became hyper‐fragmented with over half of sites losing Polylepis from the record and with coefficients of variation paralleling those of glacial times.

Main conclusions

Polylepis woodlands formed naturally patchy woodlands, rather than a continuous vegetation belt, prior to human occupation in the Andes. The main factors controlling pre‐human woodland dynamics were precipitation and landscape heterogeneity. Human activity led to hyper‐fragmentation during the last c. 1,000 years.     

Ecological and historical determinants of population genetic structure and diversity in the Mediterranean shrub Rosmarinus officinalis (Lamiaceae)

Population genetic studies of widespread Mediterranean shrubs are scarce compared with those of trees and narrow endemics or studies from phylogeographical perspectives, despite the key role these species may play in Mediterranean ecosystems. Knowledge on the effect of ecological factors in shaping their genetic patterns is also limited. In this study we investigate genetic diversity and population structure across 18 populations of Rosmarinus officinalis, a Mediterranean shrubland plant. Populations were sampled along two elevational gradients, one each on calcareous and siliceous soils in a mountain system in the eastern Iberian Peninsula, to decipher the effect of ecological factors on the genetic diversity and structure based on 11 microsatellite loci. We found overall high levels of genetic diversity and weak population structure. Genetic diversity increased with elevation, whereas population differentiation was stronger among populations growing on siliceous soils. The nested analysis of elevational gradients within soil types revealed that these general patterns were mostly driven by siliceous populations, whereas calcareous populations were more homogeneous along elevational belts. Bayesian analysis of population structure revealed genetic membership of lowland and high‐elevation populations to different genetic clusters and a higher admixture of intermediate‐elevation populations to both clusters. High‐elevation populations were less differentiated from a hypothetical ancestral cluster, suggesting the persistence of their gene pool during the Pleistocene glaciations. In contrast, lowland populations resulted from more recent divergence. We propose that life‐history and reproductive traits mostly contribute to explain the high levels of genetic diversity and weak population structure, whereas ecological and historical factors mostly contribute to the stronger differentiation of siliceous populations and a rapid expansion of R. officinalis on calcareous soils possibly mediated by human landscape transformations, © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 50–63.     

Genetic structure of Anogeissus dhofarica (Combretaceae) populations endemic to the monsoonal fog oases of the southern Arabian Peninsula

Anogeissus dhofarica (Combretaceae) is an endemic tree of the monsoon affected coastal mountains of the southern Arabian Peninsula, being the character species of the Hybantho durae–Anogeissetum dhofaricae association, a drought deciduous, monsoon forest community found only in the Dhofar region of southern Oman and the eastern Al‐Mahra region of south‐east Yemen. Due to the steep precipitation gradient from the centre to the edges in this monsoon affected area, A. dhofarica is found in two different habitat types: in continuous woodland belts of the Hawf and Dhofar mountains, and in isolated, scattered woodland patches, as found especially in the Fartak Mts (south‐east Yemen). Fifteen populations (212 individuals) from across the whole distribution area of the species were analysed using amplified fragment length polymorphism fingerprinting to: (1) evaluate the consequences of population fragmentation on the genetic diversity harboured in isolated patches versus cohering stands of the species and (2) to reconstruct the phylogeographical pattern of A. dhofarica as a consequence of oscillations in the monsoon activity during the Pleistocene and Holocene. The analysis of among‐population genetic differentiation and within‐population genetic diversity in A. dhofarica populations resulted in a lack of genetic pauperization and genetic differentiation of populations of the distinctly isolated patches of the Fartak Mts compared to the more luxurious forests of the Hawf and Dhofar regions. This is considered to be due to the high buffer capacity against the loss of genetic diversity caused by the long‐lived life‐form of the species combined with the capability to propagate clonally and the relatively recent fragmentation of Anogeissus forests into the described patches rather than due to high values of gene flow among remnant populations caused by bee pollination and anemochorical and hydrochorical diaspore dispersal. The phylogeographical pattern of the species argues for a quite recent fragmentation of a once continuous forest belt of A. dhofarica that is rather connected with climate changes in the Holocene than triggered by aridity–humidity oscillations reported for the Pleistocene. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97 , 40–51.     

Habitat fragmentation influences genetic diversity and differentiation: Fine‐scale population structure of Cercis canadensis (eastern redbud)

Forest fragmentation may negatively affect plants through reduced genetic diversity and increased population structure due to habitat isolation, decreased population size, and disturbance of pollen‐seed dispersal mechanisms. However, in the case of tree species, effective pollen‐seed dispersal, mating system, and ecological dynamics may help the species overcome the negative effect of forest fragmentation. A fine‐scale population genetics study can shed light on the postfragmentation genetic diversity and structure of a species. Here, we present the genetic diversity and population structure of Cercis canadensis L. (eastern redbud) wild populations on a fine scale within fragmented areas centered around the borders of Georgia–Tennessee, USA. We hypothesized high genetic diversity among the collections of C. canadensis distributed across smaller geographical ranges. Fifteen microsatellite loci were used to genotype 172 individuals from 18 unmanaged and naturally occurring collection sites. Our results indicated presence of population structure, overall high genetic diversity (H_E = 0.63, H_O = 0.34), and moderate genetic differentiation (F_ST = 0.14) among the collection sites. Two major genetic clusters within the smaller geographical distribution were revealed by STRUCTURE. Our data suggest that native C. canadensis populations in the fragmented area around the Georgia–Tennessee border were able to maintain high levels of genetic diversity, despite the presence of considerable spatial genetic structure. As habitat isolation may negatively affect gene flow of outcrossing species across time, consequences of habitat fragmentation should be regularly monitored for this and other forest species. This study also has important implications for habitat management efforts and future breeding programs.     

Bird community variation across <Emphasis Type="Italic">Polylepis</Emphasis> woodland fragments and matrix habitats: implications for biodiversity conservation within a high Andean landscape

The scattered and dwindling Polylepis woodlands of the high Andean global hotspot have been identified as being of particular importance to biodiversity conservation, and yet little is known of the make-up of their faunal communities, how these vary across landscapes, and how well species might tolerate matrix/edge habitats. We examined the bird communities and vegetation characteristics of Polylepis woodlands and the surrounding matrix habitats at three sites in the Cordillera Vilcanota, southern Perú (3,400–4,500 m). The vegetation structure of woodlands varied significantly across the three sites but all were dominated by two Polylepis tree species, with mossy ground cover. Matrix habitats were treeless and dominated by ground-level puna grass-steppe or boulder scree vegetation. Bird species richness and diversity, encounter rates and the number of globally-threatened and restricted-range bird species were consistently higher in the Polylepis forests, than in matrix habitat. We used canonical correspondence analysis (CCA) to identify habitat gradients across the landscape, and to classify bird species according to their association with Polylepis, the matrix or Polylepis-matrix interface. There were few matrix-restricted bird species, but around half the bird community, including fourteen threatened or restricted-range species, were Polylepis-dependant. Many of these species had very narrow niches. The Polylepis-matrix interface was dominated by species traditionally considered invasive ecological generalists. Our study illustrates the overriding importance of Polylepis interior habitats, indicating that conservation strategies for high Andean birds must focus on patch size maintenance/enlargement, enhancement of within-patch habitat quality, and efforts to safeguard connectivity of suitable habitat across what is essentially an inhospitable puna/scree matrix.     

Low genetic diversity and fragmentation effects in a wind-pollinated tree, Polylepis multijuga Plige (Rosaceae) in the high Andes

Fragmentation is predicted to increase inbreeding depression and lower the evolutionary potential of organisms by disrupting dispersal. Trees may be more resilient to fragmentation effects due to potential long-distance dispersal mechanisms that genetically connect fragments. Polylepis woodlands in the high Andes are highly fragmented and are currently the focus of reforestation and conservation efforts. Polylepis multijuga Plige (Rosaceae) is a threatened, endemic tree species in the northern Andes of Peru. Samples were collected from 371 adult trees in nine forest fragments separated by 0.5–80 km and genotyped at amplified fragment length polymorphism loci (AFLP) and chloroplast intergenic regions to determine the connectedness of fragments and their suitability for collecting seed for restoration efforts. P. multijuga is wind-pollinated and dispersed; however, genetic diversity in P. multijuga was about half that reported for other wind-pollinated species. Genetic spatial autocorrelation and patterns of chloroplast and AFLP diversity suggest seed dispersal is very limited and that wind dispersed pollen does not effectively connect all fragments. Conservation of this species will require reforestation efforts and possibly augmentation of some fragments to increase their genetic diversity. Collecting seed from multiple large fragments and from individuals separated by at least 25 m within fragments would maximize the genetic diversity of seed collections for reforestation or augmentation. Future studies of this and other Polylepis species should determine how complex topography may affect wind mediated dispersal between fragments and patterns of genetic diversity.     

Non‐timber Forest Product Harvest does not Affect the Genetic Diversity of a Tropical Tree Despite Negative Effects on Population Fitness

The level of genetic diversity in a population can affect ecological processes and plant responses to disturbance. In turn, disturbance can alter population genetic diversity and structure. Populations in fragmented and logged habitats often show reduced genetic diversity and increased inbreeding and differentiation. Long‐term harvesting of wild plants (for foliage, bark, and roots), can affect population genetic diversity by altering individual fitness and genetic contribution. Our understanding of these changes in genetic diversity due to the harvesting of plant organs is still limited. We used nine microsatellite markers to study the effect of long‐term bark and foliage harvest by Fulani people on the genetic diversity and structure of 12 populations of African mahogany (Khaya senegalensis) in Benin. We sampled 20 individuals in each population to test the effect of harvesting. For each population, we divided the samples equally between seedling and adults to test if the effects are stronger in seedlings. We found moderate genetic diversity (H_e = 0.53 ± 0.04) and weak but significant differentiation among local populations (F_ST = 0.043, P < 0.001). There was no significant effect of harvest on genetic diversity or structure, although previous work found significant negative effects of harvest on the reproduction of adults, offspring density, and population fitness. Our results suggest that demographic responses to disturbance precede a detectable genetic response. Future studies should focus on using parentage analysis to test if genotypes of harvested parents are directly represented in the offspring populations.     

Microsatellite evidence for low genetic diversity and reproductive isolation in tetraploid Centaurea seridis (Asteraceae) coexisting with diploid Centaurea aspera and triploid hybrids in contact zones

Survival of polyploids in nature depends on several factors, including competition from diploid relatives and increased genetic diversity. Unlike other reported Centaurea polyploid complexes, diploid Centaurea aspera and tetraploid Centaurea seridis coexist in hybrid zones with frequent triploid individuals. The polyploid origin of C. seridis, the genetic diversity and population structure of the three cytotypes, and the degree of genetic differentiation among them were analyzed in seven mixed‐ploidy zones, involving different subspecies and ecological conditions. Ploidy was determined by flow cytometry. Microsatellite data suggested an allopolyploid origin of C. seridis. In the contact zones, diploids and tetraploids were genetically differentiated. When compared with the related C. aspera, a low genetic diversity was observed in C. seridis, which is uncommon in tetraploids. Furthermore, although diploid individuals were grouped in a single widespread genetic cluster, tetraploids were grouped in two highly differentiated clusters and showed significant isolation by distance. This genetic pattern in C. seridis may be related to a minimal gene flow with diploid relatives and/or other genetic factors, such as rare polyploidization events, founder effects or an increased selfing rate. Neither taxonomic assignment at subspecies level, nor ecological conditions could explain the genetic differentiation between tetraploid clusters. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 82–98.     

Sex ratio rather than population size affects genetic diversity in Antennaria dioica

• Habitat fragmentation and small population size can lead to genetic erosion in threatened plant populations. Classical theory implies that dioecy can counteract genetic erosion as it decreases the magnitude of inbreeding and genetic drift due to obligate outcrossing. However, in small populations, sex ratios may be strongly male‐ or female‐biased, leading to substantial reductions in effective population size. This may theoretically result in a unimodal relationship between sex ratios and genetic diversity; yet, empirical studies on this relationship are scarce.
• Using AFLP markers, we studied genetic diversity, structure and differentiation in 14 highly fragmented Antennaria dioica populations from the Central European lowlands. Our analyses focused on the relationship between sex ratio, population size and genetic diversity.
• Although most populations were small (mean: 35.5 patches), genetic diversity was moderately high. We found evidence for isolation‐by‐distance, but overall differentiation of the populations was rather weak. Females dominated 11 populations, which overall resulted in a slightly female‐biased sex ratio (61.5%). There was no significant relationship between population size and genetic diversity. The proportion of females was not unimodally but positively linearly related to genetic diversity.
• The high genetic diversity and low genetic differentiation suggest that A. dioica has been widely distributed in the Central European lowlands in the past, while fragmentation occurred only in the last decades. Sex ratio has more immediate consequences on genetic diversity than population size. An increasing proportion of females can increase genetic diversity in dioecious plants, probably due to a higher amount of sexual reproduction.

     

Long‐term ‘islands’ in the landscape: low gene flow,effective population size and genetic divergence in the shrub Hakea oldfieldii (Proteaceae)

The genetic structure of disjunct populations is determined by founding genetic properties, demographic processes, gene flow, drift and local selection. We aim to identify the genetic consequences of natural population disjunction at regional and local scales in Hakea oldfieldii using nuclear and plastid markers to investigate long‐term effective population sizes and gene flow, and patterns of diversity and divergence, among populations. Regional divergence was significant as shown by a consistent pattern in principal coordinates, neighbor‐joining and Bayesian analyses, but divergence at the local level was also significant with localized distribution of plastid haplotypes and populations clustering separately in Bayesian analyses. Historical, recent and first‐generation gene flow was low, suggesting that recent habitat fragmentation has not reduced gene migration significantly. Genetic bottlenecks were detected in three populations. Long‐term effective population size was significantly correlated with the number of alleles/locus and observed heterozygosity, but not with census population size, suggesting that the loss of diversity is associated with long‐term changes rather than recent fragmentation. Inbreeding coefficients were significant in only three populations, suggesting that the loss of diversity is linked to drift and bottlenecks associated with demographic processes (local extinction by fires) rather than inbreeding. Historical disjunction as a result of specific ecological requirements, contraction of habitats following drying during the Pleistocene, low gene flow and changes in population size are likely to have been important forces driving divergence through isolation by distance and drift. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 319–334.     

Rural–urban gradients and the population genetic structure of woodland ground beetles

Genetic diversity and differentiation of two carabid beetle species were examined in woodlands along rural–urban gradients in two cities (Brussels, Belgium, and Birmingham, UK), based on allozymes, studied in more than 1000 beetles. Compared to Abax ater, Pterostichus madidus showed higher levels of genetic diversity but lower genetic differentiation, probably because of its ability to survive in non-forest habitats. Higher genetic diversity in both species was observed in Brussels as compared to Birmingham. However, genetic differentiation among sites was higher in Birmingham corresponding to the more extreme degree of fragmentation and isolation between the Birmingham woodlands. The isolation-by-distance model did not explain genetic differentiation among sites within the two regions. Gene diversity in P. madidus Birmingham populations was higher in smaller urban forests with a small perimeter. A similar absence of genetic erosion in smaller and more highly modified (urban) populations was also obtained for A. ater populations from Brussels, with a higher genetic diversity in sites closer to woodland edges. This unexpected result is hypothesised to be the result of an adaptive increase of genetic diversity in more heterogeneous landscapes, closer to woodland edges and in smaller and more perturbed forests.     

<Emphasis Type="Italic">Polylepis</Emphasis> woodland remnants as biodiversity islands in the Bolivian high Andes

Mountain forests deserve special attention from ecologists and conservation biologists given the ecosystem services they provide to society, and their threat under global change. In the subalpine region of the Andes, Polylepis woodlands occur as arboreal islands in a matrix of grassland and scrub. Due to overgrazing and burning, however, these woodland patches are believed to cover only 11% of their potential area in Bolivia, core area for Polylepis. We reviewed the knowledge on the species diversity for the Bolivian Polylepis woodland remnants, assessed the conservation status of the occurring species, determined their trophic niche, and related species richness with climatic variables and elevation. Based in 31 publications, we found 780 identified species occurring in Polylepis woodlands: 425 plants, 266 birds, 46 mammals, 35 butterflies and 8 reptiles. Ten of the 13 Bolivian Polylepis species, as well as 7 other plant species, 14 bird species and 4 mammal species were categorized as threatened or near threatened according to IUCN criteria. In general, plant species richness increased with increased precipitation and length of the growth season, while it decreased with increasing elevation. There was a positive relationship between bird species richness, precipitation and length of the growth season. The highest bird endemism in Polylepis woodland remnants occurred at intermediate elevations, temperatures and precipitation. Mammal species richness decreased with increasing maximum temperature. Finally, we discuss the most important knowledge gaps regarding biodiversity in Bolivian Polylepis woodland remnants.     

Temporal genetic structuring of a specialist parasitoid,Lysiphlebus hirticornis Mackauer (Hymenoptera: Braconidae) attacking a specialist aphid on tansy

In insect species characterized by inbreeding, limited dispersal, and a metapopulation structure, high genetic differentiation and reduced genetic diversity within local populations are expected. Using the model system Lysiphlebus hirticornis Mackauer, a specialist parasitoid of the tansy aphid, Metopeurum fuscoviride Stroyan (Hemiptera: Aphididae), we examined within‐site temporal population dynamics and genetics, including molecular variation at the tansy plant level. Aphid‐parasitoid dynamics were surveyed and parasitoids sampled from 72 tansy plants at 11 sites in and around Jena, Germany, over one growing season. Thereafter, parasitoid samples were genotyped at 11 polymorphic microsatellite loci. Colonization, extinction, and recolonization events occurred during the season. Allele numbers and identities were highly variable over time. When samples from all sites were pooled, allele number over all loci showed a decreasing trend with time. At the level of sites, temporal changes in genetic diversity were more variable. Analysis of molecular variance revealed that samples at the plant level explained the highest variance compared to at site level. We conclude that the genetic structuring of this insect is very fine grained (i.e. at the tansy plant level) and the temporal genetic diversity is explained by a combination of extinction and recolonization events, as well as inbreeding. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 737–749.     

Conservation genetics of the rare Iberian endemic Cheirolophus uliginosus (Asteraceae)

Cheirolophus uliginosus is a rare species, endemic to the south‐western Iberian Peninsula, and listed as a characteristic taxon from the temperate Atlantic wet heaths, a priority habitat for conservation by the European Union. The conservation status of this species in most of its distribution area is poorly known, but, in recent times, some populations have disappeared and there has been a reduction in the number of individuals in others. In this context, we analysed the effects of population size on genetic diversity, revealing that genetic erosion and inbreeding depression could be having a significant impact on smaller populations. Furthermore, we studied the patterns of genetic structure and variability at the species level, finding a strikingly low within‐population diversity and high among‐population genetic differentiation. Finally, the genetic structure analyses suggested a long and complex phylogeographical history of C. uliginosus in the region, in agreement with the climate relict status proposed for this species. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 157–171.     

Effects of population size and isolation on the genetic structure of the East African mountain white‐eye Zosterops poliogaster (Aves)

Habitat size, quality and isolation determine the genetic structure and diversity of populations and may influence their evolutionary potential and vulnerability to stochastic events. Small and isolated populations are subject to strong genetic drift and can lose much of their genetic diversity due to stochastic fixation and loss of alleles. The mountain white‐eye Zosterops poliogaster, a cloud forest bird species, is exclusively found in the high mountains of East Africa. We analysed 13 polymorphic microsatellites for 213 individuals of this species that were sampled at different points in time in three mountain massifs differing in habitat size, isolation and habitat degradation. We analysed the genetic differentiation among mountain populations and estimated the effective population sizes. Our results indicate three mountain‐specific genetic clusters. Time cohorts did not show genetic divergences, suggesting that populations are large enough to prevent strong drift effects. Effective population sizes were higher in larger and geographically interconnected habitat patches. Our findings underline the relevance of ecological barriers even for mobile species and show the importance of investigating different estimators of population size, including both approaches based on single and multiple time‐points of sampling, for the inference of the demographic status of a population. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 828–836.     

Population genetics of the olive‐winged bulbul (Pycnonotus plumosus) in a tropical urban‐fragmented landscape

With increasing urbanization, urban‐fragmented landscapes are becoming more and more prevalent worldwide. Such fragmentation may lead to small, isolated populations that face great threats from genetic factors that affect even avian species with high dispersal propensities. Yet few studies have investigated the population genetics of species living within urban‐fragmented landscapes in the Old World tropics, in spite of the high levels of deforestation and fragmentation within this region. We investigated the evolutionary history and population genetics of the olive‐winged bulbul (Pycnonotus plumosus) in Singapore, a highly urbanized island which retains <5% of its original forest cover in fragments. Combining our own collected and sequenced samples with those from the literature, we conducted phylogenetic and population genetic analyses. We revealed high genetic diversity, evidence for population expansion, and potential presence of pronounced gene flow across the population in Singapore. This suggests increased chances of long‐term persistence for the olive‐winged bulbul and the ecosystem services it provides within this landscape.     

Rapid genetic differentiation between ex situ and their in situ source populations: an example of the endangered Silene otites (Caryophyllaceae)

Ex situ cultivation in botanic gardens could be one possibility to preserve plant species diversity and genetic variation. However, old ex situ populations are often sparsely documented. We were able to retrieve three different ex situ populations and their source in situ populations of the endangered plant species Silene otites after 20–36 years of isolation. Furthermore, three additional wild populations were included in the analysis. Population genetic diversity and differentiation were analysed using AFLP markers. Genetic variation in the ex situ populations was lower than the variation found in the in situ populations. Strong differentiation (F_ST = 0.21–0.36) between corresponding in situ and ex situ populations was observed. Bayesian clustering approach also showed a distinct genetic separation between in situ and ex situ populations. The high genetic differentiation and loss of genetic diversity during spatial and temporal isolation in the ex situ populations can be attributable to small population sizes and unconscious selection during cultivation. Therefore, adequate sampling prior to ex situ cultivation and large effective population sizes are important to preserve genetic diversity. Near‐natural cultivation allowing for generation overlap and interspecific competition without artificial selection is recommended as being best for the maintenance of the genetic constitution. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, ??, ??–??.     

Long‐term drivers of change in Polylepis woodland distribution in the central Andes

Question: Is the modern patchy distribution of highly biodiverse Polylepis woodlands a consequence of human activity or natural fluctuations in environmental conditions? What are the consequences of changing climate for the tree genus Polylepis? Location: High central tropical Andes. Methods: We characterized the ecological baseline conditions for Polylepis woodlands over the last ca. 370 000 years through: (i) examination of fossil pollen records (Salar de Uyuni and Lake Titicaca) and (ii) a review of autecological information concerning Polylepis. Results: Fossil pollen data revealed fluctuations in the abundance (ca. 0‐34%) of Polylepis pollen before the arrival of humans in South America (>12 000 years ago), indicating that Polylepis did not form permanent continuous woodland before the arrival of humans and that climatic factors can drive rapid vegetation change. Autecological assessment of Polylepis revealed: (i) negative moisture balance, (ii) fire, (iii) waterlogging, and (iv) cloud cover to be critical in determining the niche space available for Polylepis. Conclusions: Polylepis niche space in the central Andes was at a maximum during warm and wet conditions in the past, but might be at a minimum during the warmer and drier than modern conditions predicted for later this century. The sensitivity to past global climate change emphasizes the need for conservation planners to consider model predictions of a warmer central Andes in the coming decades when developing planting schemes. Natural fluctuations in woodland abundance suggest the most effective way for conservation efforts to “mimic” the natural baseline would be to develop a reproductively connected patchwork of communities.