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.     

Population genetic structure of male black grouse (Tetrao tetrix L.) in fragmented vs. continuous landscapes

We investigated the association of habitat fragmentation with genetic structure of male black grouse Tetrao tetrix. Using 14 microsatellites, we compared the genetic differentiation of males among nine localities in continuous lowland habitats in Finland to the genetic differentiation among 14 localities in fragmented habitats in the Alps (France, Switzerland and Italy). In both areas, we found significant genetic differentiation. However, the average differentiation, measured as theta, was more than three times higher in the Alps than in Finland. The greater differentiation found in the Alps is probably due to the presence of mountain ridges rising above natural habitats of the species, which form barriers to gene flow, and to a higher influence of genetic drift resulting from lower effective sizes in highly fragmented habitats. The detection of isolation by distance in the Alps suggests that gene flow among populations does occur. The genetic variability measured as gene diversity HE and allelic richness A was lower in the Alps than in Finland. This could result from the higher fragmentation and/or from the fact that populations in the Alps are isolated from the main species range and have a lower effective size than in Finland. This study suggests that habitat fragmentation can affect genetic structure of avian species with relatively high dispersal propensities.     

The effects of heavy metal pollution on genetic diversity in zinc/cadmium hyperaccumulator Sedum alfredii populations

The genetic diversity and population structure of seven populations of Sedum alfredii growing in lead/zinc (Pb/Zn) mine spoils or in uncontaminated soils from eastern and southern China were investigated using random amplified polymorphic DNA (RAPD) technology. Four of the sampled sites were heavily contaminated with heavy metals (Zn, Cd, Pb), and extremely high concentrations of Zn, Cd, and Pb were found among these corresponding populations. A significant reduction of genetic diversity was detected in the mining populations. The reduction of genetic diversity could be derived from a bottleneck effect and might also be attributed to the prevalence of vegetative reproduction of the mining populations. Analysis of molecular variance (AMOVA) and the unweighted pair group method with arithmetic mean (UPGMA) tree derived from genetic distances further corroborated that the genetic differentiation between mine populations and uncontaminated populations was significant. Polymorphism with the heavy metal accumulation capability of S. alfredii probably due to the genetic variation among populations and heavy metal contamination could have more impact on the genetic diversity and population structure of S. alfredii populations than geographic distance.     

Population structure and landscape genetics in the endangered subterranean rodent Ctenomys porteousi

In order to devise adequate conservation and management strategies for endangered species, it is important to incorporate a reliable understanding of its spatial population structure, detecting the existence of demographic partitions throughout its geographical range and characterizing the distribution of its genetic diversity. Moreover, in species that occupy fragmented habitats it is essential to know how landscape characteristics may affect the genetic connectivity among populations. In this study we use eight microsatellite markers to analyze population structure and gene flow patterns in the complete geographic range of the endangered rodent Ctenomys porteousi. Also, we use landscape genetics approaches to evaluate the effects of landscape configuration on the genetic connectivity among populations. In spite of geographical proximity of the sampling sites (8–27 km between the nearest sites) and the absence of marked barriers to individual movement, strong population structure and low values of gene flow were observed. Genetic differentiation among sampling sites was consistent with a simple model of isolation by distance, where peripheral areas showed higher population differentiation than those sites located in the central area of the species’ distribution. Landscape genetics analysis suggested that habitat fragmentation at regional level has affected the distribution of genetic variation among populations. The distance of sampling sites to areas of the landscape having higher habitat connectivity was the environmental factor most strongly related to population genetic structure. In general, our results indicate strong genetic structure in C. porteousi, even at a small spatial scale, and suggest that habitat fragmentation could increase the population differentiation.     

Population size,center–periphery,and seed dispersers’ effects on the genetic diversity and population structure of the Mediterranean relict shrub Cneorum tricoccon

The effect of population size on population genetic diversity and structure has rarely been studied jointly with other factors such as the position of a population within the species’ distribution range or the presence of mutualistic partners influencing dispersal. Understanding these determining factors for genetic variation is critical for conservation of relict plants that are generally suffering from genetic deterioration. Working with 16 populations of the vulnerable relict shrub Cneorum tricoccon throughout the majority of its western Mediterranean distribution range, and using nine polymorphic microsatellite markers, we examined the effects of periphery (peripheral vs. central), population size (large vs. small), and seed disperser (introduced carnivores vs. endemic lizards) on the genetic diversity and population structure of the species. Contrasting genetic variation (H_E: 0.04–0.476) was found across populations. Peripheral populations showed lower genetic diversity, but this was dependent on population size. Large peripheral populations showed high levels of genetic diversity, whereas small central populations were less diverse. Significant isolation by distance was detected, indicating that the effect of long‐distance gene flow is limited relative to that of genetic drift, probably due to high selfing rates (F_IS = 0.155–0.887), restricted pollen flow, and ineffective seed dispersal. Bayesian clustering also supported the strong population differentiation and highly fragmented structure. Contrary to expectations, the type of disperser showed no significant effect on either population genetic diversity or structure. Our results challenge the idea of an effect of periphery per se that can be mainly explained by population size, drawing attention to the need of integrative approaches considering different determinants of genetic variation. Furthermore, the very low genetic diversity observed in several small populations and the strong among‐population differentiation highlight the conservation value of large populations throughout the species’ range, particularly in light of climate change and direct human threats.     

Population structure and genetic diversity of trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>) above and below natural and man-made barriers in the Russian River,California

The effects of landscape features on gene flow in threatened and endangered species play an important role in influencing the genetic structure of populations. We examined genetic variation of trout in the species Oncorhynchus mykiss at 22 microsatellite loci from 20 sites in the Russian River basin in central California. We assessed relative patterns of genetic structure and variation in fish from above and below both natural (waterfalls) and man-made (dams) barriers. Additionally, we compared sites sampled in the Russian River with sites from 16 other coastal watersheds in California. Genetic variation among the 20 sites sampled within the Russian River was significantly partitioned into six groups above natural barriers and one group consisting of all below barrier and above dam sites. Although the below-barrier sites showed moderate gene flow, we found some support for sub-population differentiation of individual tributaries in the watershed. Genetic variation at all below-barrier sites was high compared to above-barrier sites. Fish above dams were similar to those from below-barrier sites and had similar levels of genetic diversity, indicating they have not been isolated very long from below-barrier populations. Population samples from above natural barriers were highly divergent, with large F _st values, and had significantly lower genetic diversity, indicating relatively small population sizes. The origins of populations above natural barriers could not be ascertained by comparing microsatellite diversity to other California rivers. Finally, below-barrier sites farther inland were more genetically differentiated from other watersheds than below-barrier sites nearer the river’s mouth.     

Molecular biodiversity in the moss <Emphasis Type="Italic">Leptodon smithii</Emphasis> (Neckeraceae) in relation to habitat disturbance and fragmentation

Bryophytes seem particularly suitable to investigate genetic diversity in relation to habitat disturbance due to their large employment as bioindicators and to the recent application of molecular markers to moss population studies. Genetic variation and structure were analysed in seven urban, extraurban and remote populations of Leptodon smithii, an epiphytic moss of Quercus ilex, a phanerogamic species of Mediterranean climax vegetation. A total of 210 individual shoots were DNA extracted and amplified with internal simple sequence repeat (ISSR) primers, and 54 haplotypes were identified. An uneven distribution of haplotype number and frequencies was observed among sites, with a higher number of haplotypes and more homogeneous haplotype frequencies in the extraurban/remote populations. Molecular diversity indices were overall higher in the extraurban sites than in the urban ones. Multilocus linkage disequilibrium values were in line with the occurrence of sexual/asexual reproduction in the seven populations. The isolation-by-distance model was not supported by Mantel test among sites; however, within-population fixation index (F_ST) highlighted a clear relation between genetic and physic distances among trees, suggesting a limited dispersal range for L. smithii’s spores. The genetic structure was mainly affected by population size, wood structure and extent, and genetic drift consequent to habitat fragmentation and human-induced disturbance.     

Allozyme variation in the annual weed species complexPolygonum aviculare (Polygonaceae) in relation to ploidy level and colonizing ability

Variation at six polymorphic enzymatic loci was studied in 50 populations of the selfing annualPolygonum aviculare from Belgium. The results show that theP. aviculare complex has an allopolyploid origin and comprises two main genetic entities, viz.P. aviculare subsp.depressum (2n = 4x = 40), restricted to urban sites subject to trampling stress, andP. aviculare subsp.aviculare (2n = 4x = 40, 2n = 6x = 60), with a wider ecological amplitude. The latter had a higher genetic diversity and a higher frequency of fixed heterozygosity than the former. WithinP. aviculare subsp.aviculare, genetic diversity and ecological amplitude correlated positively with ploidy level. Additionally, stronger genetic differentiation among and lower variation within populations was found in urban areas than in cultivated fields.     

南方红豆杉迁地保护小种群适应性进化机制研究

为了解南方红豆杉迁地保护种群的适应性进化机制,以南京中山植物园内南方红豆杉迁地保护栽培种群和扩散的衍生种群为材料,以引种初始地江西野生种群为对照,对南方红豆杉群落的结构、遗传多样性及遗传结构进行分析和研究。结果表明,南方红豆杉野生种群和迁地保护种群均维持着较高水平的遗传多样性,其中野生种群遗传多样性稍高于迁地保护小种群,但迁地保护种群中南方红豆杉个体密度大于野生种群。同时,种群内的遗传变异所占比例大于种群间的。整体来看,南方红豆杉迁地保护种群还处于演替早期,存在不明显的奠基者效应,有进一步演替发展的可能。     

Regional and local spatial genetic structure of Siberian primrose populations in Northern Europe

We have investigated the local and regional scale genetic structure of Siberian primrose (Primula nutans) populations in Northern Europe. The genetic diversity and structure of fifteen populations sampled from the Bothnian Bay in Finland, the Barents Sea in Norway and the White Sea in Russia were assessed using eleven microsatellite markers. We investigated the distribution of genetic variation within and between populations, and studied the local genetic structure using spatial autocorrelation analysis. We found very low genetic and allelic diversity in the Bothnian Bay and Barents Sea populations, and only slightly higher in the White Sea population. The level of genetic differentiation between the regions was very high, whereas differentiation between the populations within the regions was moderate. We found no spatial structuring of populations in any region suggesting efficient dispersal on a local scale. Clonal reproduction seemed to have no effect on genetic structure.     

Inbreeding depression and the maintenance of genetic load in Melitaea cinxia metapopulations

The effects of inbreeding on fitness and themaintenance of genetic load in metapopulationsof the endangered Glanville fritillarybutterfly (Melitaea cinxia) were examinedin four laboratory experiments. In FinlandM. cinxia occurs as a large metapopulationconsisting of small local populations with fastturnover, whereas in southern France thespecies has a more continuous populationstructure. In the experiments, we compared theperformance of crosses between full sibs,crosses between members of different familieswithin populations, and crosses betweenindividuals from different populations. Theseexperiments were replicated using insects fromtwo different regions, Finland and southernFrance, between which the frequency of naturalinbreeding should differ substantially becauseof differing population structure. In Finnishbutterflies, the rate of successful mating waslower among insects derived from small thanfrom large natural populations, probablyreflecting the effect of past inbreedinghistory. Mating between full sibs lowered egghatching rate in all experiments. Thisreduction of egg hatching rate was more severeamong French butterflies with a more continuouspopulation structure than among Finnishbutterflies with small naturally fragmentedpopulations and with a history of repeatedrounds of inbreeding in the past. This resultsuggests that recurrent inbreeding has led topartial purging of deleterious recessives fromthe Finnish metapopulation. Nonetheless,substantial genetic load still remains in thismetapopulation, and we discuss possible reasonswhy this should be the case.     

A comparison of the genetic diversity in Dipteronia sinensis Oliv. and Dipteronia dyeriana Henry

Dipteronia is an endemic genus to China and includes only two species, Dipteronia sinensis and D. dyeriana. Based on random amplified polymorphic DNA (RAPD) markers, a comparative study of the genetic diversity and genetic structure of Dipteronia was performed. In total, 128 and 103 loci were detected in 17 D. sinensis populations and 4 D. dyeriana populations, respectively, using 18 random primers. These results showed that the proportions of polymorphic loci for the two species were 92.97% and 81.55%, respectively, indicating that the genetic diversity of D. sinensis was higher than that of D. dyeriana. Analysis, based on similarity coefficients, Shannon diversity index and Nei gene diversity index, also confirmed this result. AMOVA analysis demonstrated that the genetic variation of D. sinensis within and among populations accounted for 56.89% and 43.11% of the total variation, respectively, and that of D. dyeriana was 57.86% and 42.14%, respectively. The Shannon diversity index and Nei gene diversity index showed similar results. The abovementioned characteristics indicated that the genetic diversity levels of these two species were extremely similar and that the interpopulational genetic differentiation within both species was relatively high. Analysis of the genetic distance among populations also supported this conclusion. Low levels of interpopulational gene flow within both species were believed to be among the leading causes for the above-mentioned phenomenon. The correlation analysis between genetic and geographical distances showed the existence of a remarkably significant correlation between the genetic distance and the longitudinal difference among populations of D. sinensis (p < 0.01), while no significant correlation was found between genetic and geographical distances among populations of D. dyeriana. This indicated that genetic distance was correlated with geographical distances on a large scale rather than on a small scale. This result may be related to differences in the selection pressure on species by their habitats with different distribution ranges. We suggest that in situ conservation efforts should focus on establishing more sites to protect the natural populations and their habitats. Ex situ conservation efforts should focus on enhancing the exchange of seeds and seedlings among populations to facilitate gene exchange and recombination, and to help conserve genetic diversity. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(5): 785–792 [译自: 植物生态学报, 2005, 29(5): 785–792]     

Genetic Diversity and Geographic Differentiation in the Threatened Species Dysosma pleiantha in China as Revealed by ISSR Analysis

Dysosma pleiantha, an important threatened medicinal plant species, is restricted in distribution to southeastern China. The species is capable of reproducing both sexually and asexually. In this study, inter-simple sequence repeat marker data were obtained and analyzed with respect to genetic variation and genetic structure. The extent of clonality, together with the clonal and sexual reproductive strategies, varied among sites, and the populations under harsh ecological conditions tended to have large clones with relatively low clonal diversity caused by vegetative reproduction. The ramets sharing the same genotype show a clumped distribution. Across all populations surveyed, average within-population diversity was remarkably low (e.g., 0.111 for Nei’s gene diversity), with populations from the nature reserves maintaining relatively high amounts of genetic diversity. Among all populations, high genetic differentiation (AMOVA: Φ_ST = 0.500; Nei’s genetic diversity: G _ST = 0.465, Bayesian analysis: Φ_B = 0.436) was detected, together with an isolation-by-distance pattern. Low seedling recruitment due to inbreeding, restricted gene flow, and genetic drift are proposed as determinant factors responsible for the low genetic diversity and high genetic differentiation observed.     

Can small wildlife conservancies maintain genetically stable populations of large mammals? Evidence for increased genetic drift in geographically restricted populations of Cape buffalo in East Africa

The Cape buffalo (Syncerus caffer caffer) is one of the dominant and most widespread herbivores in sub‐Saharan Africa. High levels of genetic diversity and exceptionally low levels of population differentiation have been found in the Cape buffalo compared to other African savannah ungulates. Patterns of genetic variation reveal large effective population sizes and indicate that Cape buffalos have historically been interbreeding across considerable distances. Throughout much of its range, the Cape buffalo is now largely confined to protected areas due to habitat fragmentation and increasing human population densities, possibly resulting in genetic erosion. Ten buffalo populations in Kenya and Uganda were examined using seventeen microsatellite markers to assess the regional genetic structure and the effect of protected area size on measures of genetic diversity. Two nested levels of genetic structure were identified: a higher level partitioning populations into two clusters separated by the Victoria Nile and a lower level distinguishing seven genetic clusters, each defined by one or two study populations. Although relatively small geographic distances separate most of the study populations, the level of genetic differentiation found here is comparable to that among pan‐African populations. Overall, correlations between conservancy area and indices of genetic diversity suggest buffalo populations inhabiting small parks are showing signs of genetic erosion, stressing the need for more active management of such populations. Our findings raise concerns about the future of other African savannah ungulates with lower population sizes and inferior dispersal capabilities compared with the buffalo.     

ORGANIZATION OF GENETIC DIVERSITY WITHIN AND AMONG POPULATIONS OF GLEDITSIA TRIACANTHOS (LEGUMINOSAE)

This study describes levels of allozyme diversity and patterns of genetic structure within and among populations of honey locust (Gleditsia triacanthos L.). Using data from starch gel electrophoresis, honey locust was found to have high genetic diversity within populations (HM_E = 0.198), and low, but significant genetic differentiation among populations (Γ_ST = 0.059). Temporal and spatial substructuring were also investigated in two populations from eastern Kansas. Few genetic differences were found among nine age classes in one population and between juveniles and adults in the second population. Separate autocorrelation analyses of juveniles and adults revealed significant spatial substructuring in both age classes. Three conclusions were reached from these analyses. First, even small amounts of clonal growth can cause large increases in the amount of substructuring in populations. Second, spatial genetic substructuring among juveniles at both sites most likely represents the presence of family groups. Last, the overall level of spatial genetic substructuring at both sites was somewhat greater in the juvenile classes than in the nonclonal adult classes. This latter conclusion is consistent with theoretical studies suggesting that limited gene movement causes a steady increase in spatial structure from generation to generation.     

Genetic Structure of Przewalski’s Rock Partridge (Alectoris magna) Populations in the Longzhong Loess Plateau, China

In this paper, we have analyzed the nuclear DNA of Alectoris magna samples, collected from the Longzhong Loess Plateau. We used allelic variation at eight microsatellite markers to describe the genetic structure of A. magna populations. The primary goal of this study was to examine the population genetic structure and determine the extent of population differentiation among populations of A. magna. The average value of H _E (0.455) was smaller than H _O (0.477), and there was a heterozygote deficit at the MCW135 locus in the Lanzhou population and the Beidao population. The AB063167 locus in each population (except that of Jingyuan) was not in equilibrium (P < 0.05). The Lixian edge population had a lower proportion of genetic diversity than the central geographic populations; the Haiyuan and Jingyuan populations had higher genetic diversity than the central geographic populations. Analysis of population structure revealed clear differentiation among the eight populations of A. magna, suggesting strong isolation of these populations and correspondingly low levels of migration or gene flow. The A. magna populations of Longzhong Loess Plateau are separated into eastern and western populations by a clustering chart. Genetic data indeed suggest that patterns of speciation and population diversification of A. magna in the Longzhong Plateau have been affected by the stability of the climate, natural selection, and human intervention.     

Large mainland populations of South Island robins retain greater genetic diversity than offshore island refuges

For conservation purposes islands are considered safe refuges for many species, particularly in regions where introduced predators form a major threat to the native fauna, but island populations are also known to possess low levels of genetic diversity. The New Zealand archipelago provides an ideal system to compare genetic diversity of large mainland populations where introduced predators are common, to that of smaller offshore islands, which serve as predator-free refuges. We assessed microsatellite variation in South Island robins (Petroica australis australis), and compared large mainland, small mainland, natural island and translocated island populations. Large mainland populations exhibited more polymorphic loci and higher number of alleles than small mainland and natural island populations. Genetic variation did not differ between natural and translocated island populations, even though one of the translocated populations was established with five individuals. Hatching failure was recorded in a subset of the populations and found to be significantly higher in translocated populations than in a large mainland population. Significant population differentiation was largely based on heterogeneity in allele frequencies (including fixation of alleles), as few unique alleles were observed. This study shows that large mainland populations retain higher levels of genetic diversity than natural and translocated island populations. It highlights the importance of protecting these mainland populations and using them as a source for new translocations. In the future, these populations may become extremely valuable for species conservation if existing island populations become adversely affected by low levels of genetic variation and do not persist.     

Development of genetic diversity,differentiation and structure over 500 years in four ponderosa pine populations

Population history plays an important role in shaping contemporary levels of genetic variation and geographic structure. This is especially true in small, isolated range‐margin populations, where effects of inbreeding, genetic drift and gene flow may be more pronounced than in large continuous populations. Effects of landscape fragmentation and isolation distance may have implications for persistence of range‐margin populations if they are demographic sinks. We studied four small, disjunct populations of ponderosa pine over a 500‐year period. We coupled demographic data obtained through dendroecological methods with microsatellite data to discern how and when contemporary levels of allelic diversity, among and within‐population levels of differentiation, and geographic structure, arose. Alleles accumulated rapidly following initial colonization, demonstrating proportionally high levels of gene flow into the populations. At population sizes of approximately 100 individuals, allele accumulation saturated. Levels of genetic differentiation among populations (F_ST and Jost's D_est) and diversity within populations (F_IS) remained stable through time. There was no evidence of geographic genetic structure at any time in the populations' history. Proportionally, high gene flow in the early stages of population growth resulted in rapid accumulation of alleles and quickly created relatively homogenous genetic patterns among populations. Our study demonstrates that contemporary levels of genetic diversity were formed quickly and early in population development. How contemporary genetic diversity accumulates over time is a key facet of understanding population growth and development. This is especially relevant given the extent and speed at which species ranges are predicted to shift in the coming century.     

Strong intraspecific variation in genetic diversity and genetic differentiation in Daphnia magna: the effects of population turnover and population size

Theory predicts that genetic diversity and genetic differentiation may strongly vary among populations of the same species depending on population turnover and local population sizes. Yet, despite the importance of these predictions for evolutionary and conservation issues, empirical studies comparing high‐turnover and low‐turnover populations of the same species are scarce. In this study, we used Daphnia magna, a freshwater crustacean, as a model organism for such a comparison. In the southern/central part of its range, D. magna inhabits medium‐sized, stable ponds, whereas in the north, it occurs in small rock pools with strong population turnover. We found that these northern populations have a significantly lower genetic diversity and higher genetic differentiation compared to the southern/central populations. Total genetic diversity across populations was only about half and average within‐population diversity only about a third of that in southern/central populations. Moreover, an average southern population contains more genetic diversity than the whole metapopulation system in the north. We based our analyses both on silent sites and microsatellites. The similarity of our results despite the contrasting mutation rates of these markers suggests that the differences are caused by contemporary rather than by historical processes. Our findings show that variation in population turnover and population size may have a major impact on the genetic diversity and differentiation of populations, and hence may lead to differences in evolutionary processes like local adaptation, hybrid vigour and breeding system evolution in different parts of a species range.     

Genetic diversity and population structure in Malus sieversii, a wild progenitor species of domesticated apple

Malus sieversii (Lebed.) M. Roem. is a wild progenitor species of the domesticated apple. It is found across a mountainous region of central Asia and has been the focus of several collection expeditions by the USDA-ARS-National Plant Germplasm System. This study used microsatellite variation at seven loci to estimate diversity and differentiation within M. sieversii using several complimentary approaches. Multilocus genotypes were amplified from 949 individuals representing seedling trees from 88 half-sib families from eight M. sieversii populations collected in Kazakhstan. Apportioning of genetic variation was estimated at both the family and site level. Analyses using a hierarchical model to estimate F _st showed that differentiation among individual families is more than three times greater than differentiation among sites. In addition, average gene diversity and allelic richness varied significantly among sites. A rendering of a genetic network among all sites showed that differentiation is largely congruent with geographical location. In addition, nonhierarchical Bayesian assignment methods were used to infer genetic clusters across the collection area. We detected four genetic clusters in the data set. The quality of these assignments was evaluated over multiple Markov Chain Monte Carlo runs using both posterior likelihood and stability of the assignments. The spatial pattern of genetic assignments among the eight collection sites shows two broadly distributed and two narrowly distributed clusters. These data indicate that the southwestern collection sites are more admixed and more diverse than the northern sites.