Genetic variation of Ardisia crenata in south China revealed by nuclear microsatellite

Ardisia crenata Sims, one of the most widely distributed Ardisia in the world, is an important ornamental and medicinal plant species. Using 7 polymorphic nuclear microsatellite loci, we studied the genetic variation of 20 natural populations of A. crenata across its distribution centre, the south China. Significant deviation from Hardy-Weinberg equilibrium in all populations and at all loci were detected, and the fixation index was high (F_IS = 0.725), indicating that inbreeding may be dominant in the mixed mating system of this self-compatible species. The average genetic diversity within populations was relatively low (H_S = 0.321). There was significant genetic differentiation among populations (F_ST = 0.583), which may be resulted from high level of inbreeding and low level of gene flow. A. crenata in south China can be roughly divided into eastern group and western group, consistent with the floristic division of Sino-Himalayan forest subkingdom and Sino-Japanese forest subkingdom. It was suggested that there may be separated glacial refugia in each region.     

浙江天童国家森林公园红凉伞交配系统研究

 交配系统是影响植物种群遗传结构的重要因素之一,测定植物的交配系统不仅可以了解物种的繁殖格局,而且也有助于预测生境条件发生变化(如生境片断化)时物种遗传结构的变化趋势。红凉伞是常绿阔叶林伴生小灌木,雌雄同花。采用水平切片淀粉凝胶电泳法分析种子萌发幼苗的基因型,结合Ritland异交率估算模型(MLT),测定了浙江天童国家森林公园红凉伞的交配系统,共采用了3个酶位点(Adh-1,Fe-2和Amp-2)。两个红凉伞种群的异交率均大于1,分别为1.055和1.159,可能是由于处理过程中将小的集群合并处理的结果,因为小集群内家系数量少,无法计算异交率。计算的家系异交率大多很大,只是在小集群内存在异交率低的家系,表明当红凉伞聚生形成的集群内开花个体数少时,异交率将降低。分析了常绿阔叶林片断化对红凉伞种群交配系统的影响。     

极度濒危植物五针白皮松的保护遗传学研究

用随机扩增多态(RAPD)方法对极度濒危植物五针白皮松(Pinus squamata X.W.Li)的遗传多样性和居群遗传结构进行了研究。14个随机引物共获得93条RAPD谱带,其中6条为多态带,多态位点百分率仅为6．45％,遗传多样性极低。Shannon指数I和Nei指数h在种内也只有0．020和0．030,两个亚居群间(半阴坡亚居群与半阳坡亚居群)遗传分化程度不高,遗传分化系数Gst只有0．110,与大多数松科植物近似,居群每代迁移数为4．032。五针白皮松极低的遗传多样性可能是由于它在演化过程中遭受过严重的灾害,造成严重的瓶颈效应,丧失其大部分遗传变异。在随后的演化过程中由于遗传漂变、自交衰退等小种群现象,导致遗传多样性的进一步丧失。另外,阔叶树种对其生存的挤压和人类的干扰也是导致五针白皮松遗传多样性降低的因素之一。本文最后对该结果的保护生物学意义进行了评价。     

Species diversity and population density affect genetic structure and gene dispersal in a subtropical understory shrub

Aims The dispersal of pollen and seeds is spatially restricted and may vary among plant populations because of varying biotic interactions, population histories or abiotic conditions. Because gene dispersal is spatially restricted, it will eventually result in the development of spatial genetic structure (SGS), which in turn can allow insights into gene dispersal processes. Here, we assessed the effect of habitat characteristics like population density and community structure on small-scale SGS and estimate historical gene dispersal at different spatial scales.Methods In a set of 12 populations of the subtropical understory shrub Ardisia crenata, we assessed genetic variation at 7 microsatellite loci within and among populations. We investigated small-scale genetic structure with spatial genetic autocorrelation statistics and heterogeneity tests and estimated gene dispersal distances based on population differentiation and on within-population SGS. SGS was related to habitat characteristics by multiple regression.Important findings The populations showed high genetic diversity (H e = 0.64) within populations and rather strong genetic differentiation (F ′ ST = 0.208) among populations, following an isolation-by-distance pattern, which suggests that populations are in gene flow–drift equilibrium. Significant SGS was present within populations (mean Sp = 0.027). Population density and species diversity had a joint effect on SGS with low population density and high species diversity leading to stronger small-scale SGS. Estimates of historical gene dispersal from between-population differentiation and from within-population SGS resulted in similar values between 4.8 and 22.9 m. The results indicate that local-ranged pollen dispersal and inefficient long-distance seed dispersal, both affected by population density and species diversity, contributed to the genetic population structure of the species. We suggest that SGS in shrubs is more similar to that of herbs than to trees and that in communities with high species diversity gene flow is more restricted than at low species diversity. This may represent a process that retards the development of a positive species diversity–genetic diversity relationship.     

Distribution of genetic diversity among disjunct populations of the rare forest understory herb, Trillium reliquum

We assessed genetic diversity and its distribution in the rare southeastern US forest understory species, Trillium reliquum. In all, 21 loci were polymorphic (PS=95.5%) and the mean number of alleles per polymorphic locus was 3.05. However, genetic diversity was relatively low (Hes=0.120) considering the level of polymorphism observed for this outcrossing species. A relatively high portion of the genetic diversity (29.7%) was distributed among populations. There was no relationship between population size and genetic diversity, and we did not detect significant inbreeding. These results are best explained by the apparent self-incompatibility of this species, its longevity and clonal reproduction. To address questions regarding the history of T. reliquum's rarity, we compared results for T. reliquum with that of its more common and partially sympatric congener, T. cuneatum. Despite shared life history traits and history of land use, we observed significant genetic differences between the two species. Although T. cuneatum contains slightly lower polymorphism (Ps=85%), we detected significantly higher genetic diversity (Hes=0.217); most of its genetic diversity is contained within its populations (GST=0.092). Our results suggest that not only is there little gene flow among extant T. reliquum populations, but that rarity and population isolation in this species is of ancient origins, rather than due to more recent anthropogenic fragmentation following European colonization. The Chattahoochee River was identified as a major barrier to gene exchange.     

Fine-scale spatial genetic structure and allozymic diversity in natural populations of <Emphasis Type="Italic">Ocotea catharinensis</Emphasis> Mez. (Lauraceae)

In order to establish a strategy for conservation, the distribution of genetic diversity in four natural populations of Ocotea catharinensis in the Brazilian Atlantic rain forest was investigated using 18 allozyme loci. Estimates of the average number of alleles per loci (2.2), percentage of polymorphic loci (83.3%) and expected genetic diversity (0.427) in adult individuals were high; suggesting that all populations have genetic potential for conservation. The inbreeding within populations ([^(f)] = - 0.0 1 1 \hat{f} = - 0.0 1 1 ) and the total inbreeding ([^(F)] = 0. 1 3 3 \hat{F} = 0. 1 3 3 ) suggest population structure, since a high level of divergence among populations ( [^(q)]_\textP = 0. 1 4 3 \hat{\theta }_{\text{P}} = 0. 1 4 3 ) was also detected. Significant values of spatial genetic structure were found inside the four populations. This study demonstrates that the realized gene flow among the remaining populations of O. catharinensis is not sufficient to stop population divergence due to genetic drift and local selection, which threatens the future viability of this species.     

Genetic variation of Avicennia marina (Forsk.) Vierh. (Avicenniaceae) in Vietnam revealed by microsatellite and AFLP markers

Genetic variation of Avicennia marina in the costal area of Vietnam was examined using microsatellite and AFLP markers. By using five microsatellite loci a total of 21 alleles were detected. The average number of alleles per locus per population ranged from 1.667 to 3.000. The observed heterozygosity varied from 0.180 to 0.263, with an average of 0.210 indicating relatively low level of genetic variation comparing to the previous studies on A. marina in the worldwide range. The expected heterozygosity was larger than the observed heterozygosity leading to positive inbreeding coefficients in all the six populations. Highly significant departures from Hardy-Weinberg Equilibrium were detected in four populations. AFLP analysis revealed a total of 386 loci, of which 232 (60.1%) were polymorphic. In congruent with microsatellite markers relatively low levels of genetic variation were detected at both gene and nucleotide levels (H = 0.086; pi = 0.0054). Reduced level of genetic variation was found in the central population, and in the southern populations. Both microsatellite and AFLP markers revealed large genetic differentiation (F(ST) = 0.262 and 0.338, respectively) indicating strong genetic structure among regional populations. Pairwise genetic distance by AFLP showed two populations in the north and the other two in the south are closely related each other.     

Temporal and spatial genetic structure in Vitellaria paradoxa (shea tree) in an agroforestry system in southern Mali

Ten microsatellite loci were used to investigate the impact of human activity on the spatial and temporal genetic structure of Vitellaria paradoxa (Sapotaceae), a parkland tree species in agroforestry systems in southern Mali. Two stands (forest and fallow) and three cohorts (adults, juveniles and natural regeneration) in each stand were studied to: (i) compare their levels of genetic diversity (gene diversity, HE; allelic richness, Rs; and inbreeding, FIS); (ii) assess their genetic differentiation (FST); and (iii) compare their levels of spatial genetic structuring. Gene diversity parameters did not vary substantially among stands or cohorts, and tests for bottleneck events were nonsignificant. The inbreeding coefficients were not significantly different from zero in most cases (FIS = -0.025 in forest and 0.045 in fallow), suggesting that the species is probably outbreeding. There was a weak decrease in F(IS) with age, suggesting inbreeding depression. Differentiation of stands within each cohort was weak (FST = 0.026, 0.0005, 0.010 for adults, juveniles and regeneration, respectively), suggesting extensive gene flow. Cohorts within each stand were little differentiated (FST = -0.001 and 0.001 in forest and fallow, respectively). The spatial genetic structure was more pronounced in fallow than in forest where adults showed no spatial structuring. In conclusion, despite the huge influence of human activity on the life cycle of Vitellaria paradoxa growing in parkland systems, the impact on the pattern of genetic variation at microsatellite loci appears rather limited, possibly due to the buffering effect of extensive gene flow between unmanaged and managed populations.     

Genetic diversity and the mating system of a rare Mexican pinon, Pinus pinceana, and a comparison with Pinus maximartinezii (Pinaceae)

Weeping pi?on (Pinus pinceana) has a restricted and fragmented range, trees are widely scattered within populations, and reproduction is limited. Nevertheless, genetic diversity was high; based on 27 isozyme loci in 18 enzyme systems, unbiased expected heterozygosity averaged 0.174. Differentiation also was high (F(ST) = 0.152), reflecting isolation between southern, central, and northern fragments of the range. Among populations in the northern fragment, F(ST) was only 0.056, and the number of migrants per generation (Nm) was 4.21, which should preclude fixation. Nm between central and southern populations or between them and populations in the northern fragment was lower, 0.99-1.66, indicating a degree of genetic isolation. Multilocus outcrossing rates (t(m)) ranged from 0.836 in the south to 0.897 in the north. Therefore, selfing is low but statistically significant. The equilibrium inbreeding coefficient (F(e)) calculated from t(m) was in good agreement with observed inbreeding coefficients, suggesting that weeping pi?on may be near equilibrium with respect to inbreeding and selection against selfed trees. Weeping pi?on was variable at all loci polymorphic in maxipi?on (Pinus maximartinezii) and, therefore, qualifies as a possible progenitor of maxipi?on. Because of the high level of diversity, reasonable levels of gene flow within the northern fragment of weeping pi?on's range, high rates of outcrossing, and, perhaps, only weak selection against inbred trees, protection in reserves would be a viable option for conservation.     

云杉天然群体遗传多样性的等位酶变异

采用等位酶淀粉凝胶电泳和聚丙烯酰胺凝胶电泳技术对中国西部亚高山特有树种云杉(Picea asperata)10个天然群体的300个个体的遗传多样性和遗传分化进行研究。对8个酶系统17个酶位点(27个等位基因)的检测分析结果表明,10个位点为单态位点,云杉具有中等偏低的遗传变异水平。群体水平上的遗传多样性指标分别为:多态位点的百分率P_P=29.41%~41.18%,等位基因平均数A_P=1.4~1.6,平均期望杂合度H_ep=0.06~0.131;种级水平的遗传多样性指标分别为:P_s=41.18%,A_s=1.2,H_es=0.138。10个群体的群体水平的观测杂合度为0.094 3,期望杂合度为0.096 4;10个群体中,7个多态位点的单位点的观测杂合度(H_o)的均值为0.229(变幅为0.142 9~0.342 9),期望杂合度(H_e)的均值为0.234 1(变幅为0.160 8~0.317 3), 云杉天然群体间遗传分化度(F_ST)为0.311,云杉群体间变异占总变异的31.1%,基因流低(N_m=0.553 9),说明群体间的基因交流有限。异交率高(t=0.957),近交率低(F_is=0.005),这些研究结果表明:云杉群体间等位基因的频率分化显著,其它云杉属树种基因的渐渗、群体微生境差异和不同强度的选择压力可能是造成群体间分化显著的主要原因;Fdh-2-B基因与综合生态梯度值呈显著的负相关(r=-0.661 1^*),H_e与经度呈显著负相关(r=-0.683^*),云杉群体间的地理和遗传距离相关不显著。10个群体均含有绝大部分等位基因,且群体间分化很大,应加以重点保护和管理,作为云杉种质资源原地保存的基地和该树种进一步遗传改良的重要育种群体。     

Interspecific genetic variability of the oyster mushroom Pleurotus ostreatus as revealed by allozyme gene analysis

Allozyme variation in natural populations of basidiomycetes fungus Pleurotus ostreatus (88 individuals) from three regions of central Russia was studied. The species was shown to have 92.86% of polymorphic allozyme loci and expected heterozygosity He = 0.49. The mean number of alleles per locus was 3.5. The genetic differences among populations were supported by F-statistics (FST = 0.750). The low level of inbreeding (FIS = 0.018) suggests that the P. ostreatus populations are panmictic, and the main reproduction mode involves basidiospores dispersing at long distances. Using cluster analysis, geographically isolated populations and intersterile groups were differentiated within the complex P. ostreatus species.     

High levels of allozyme variation within populations and low allozyme divergence within and among species of Hemerocallis (Liliaceae)

Thirty populations from five species of Hemerocallis in Korea were analyzed by starch gel electrophoresis to measure genetic diversity and to determine genetic population structure and the amount of genetic divergence within and between species at 12 isozyme loci. In addition, Moran's I spatial autocorrelation statistics were used to examine the spatial distribution of allozyme polymorphisms in populations of H. thunbergii and H. hakuunensis. Populations of five Korean species maintain high levels of genetic variation and little differentiation among populations and species. Mean expected heterozygosities range from 0.165 in H. hongdoensis, an island endemic, to 0.265 in H. taeanensis, and a total of 81 alleles across the 12 loci were detected in the five species. G(ST) values for each of the five species were low, ranging from 0.051 in H. taeanensis to 0.078 in H. hakuunensis. Mean intraspecific Nei's genetic identities (I) between populations of the five species were all above 0.97. However, a considerable level of heterozygote deficiencies within populations was detected, ranging from 0.242 to 0.411 measured as F(IS) statistics. This deficiencies may be due to inbreeding, limited pollen and seed dispersal, or from the pooling of subpopulations that differ in allele frequencies. A small spatial scale population substructuring (<12 m) was found in H. thunbergii and H. hakuunensis. A group of populations from each of the five previously designated Hemerocallis species (based on their morphology, ecology, and phenology) agrees with our allozyme data, though pairwise comparisons among species had high I values (from 0.862, H. middendorffii vs. H. hongdoensis, to 0.969, H. thunbergii vs. H. taeanensis). This is attributed to the presence of the same high-frequency alleles in different species at seven loci. In addition, no "diagnostic allele" that appears in all populations of one species, but is absent in other species, was detected at the 12 isozyme loci. These all suggest that species of Hemerocallis in Korea may have recently derived from an ancestor or progenitor harboring high levels of genetic diversity.     

Conservation of long-lived perennial forest herbs in an urban context: <Emphasis Type="Italic">Primula elatior</Emphasis> as study case

Urban forests are generally fragmented in small isolated remnants, embedded in an inhospitable human-used matrix, and incur strong anthropogenic pressures (recreational activities, artificialization, pollution and eutrophication). These lead to particularly high constraints even for common forest herbs, whose genetic response may depend on life-history traits and population demographic status. This study investigated genetic variation and structure for 20 allozyme loci in 14 populations of Primula elatior, a self-incompatible long-lived perennial herb, occurring in forest fragments of Brussels urban zone (Belgium), in relation to population size and young plants recruitment rate. Urban populations of P. elatior were not genetically depauperate, but the small populations showed reduced allelic richness. Small populations showing high recruitment rates—and therefore potential rejuvenation—revealed lower genetic diversity (H _o and H _e) than those with low or no recruitment. No such pattern was observed for the large populations. There was a significant genetic differentiation among populations within forest fragments (F _SC = 0.052, P < 0.001), but not between fragments (F _CT = 0.002, P > 0.10). These findings suggest restricted gene flow among populations within fragments and local processes (genetic drift, inbreeding) affecting small populations, strengthened when there is recruitment. Urban forest populations of long-lived perennial herbs can be of conservation value. However, restoration of small populations by increasing population size through regeneration by seedling recruitment may lead to negative genetic consequences. Additional management, aiming to restore gene flow among populations, may need to be applied to compensate the loss of genetic diversity and to reduce inbreeding.     

中国针茅属植物的地理分布

本文论述了中国针茅属植物的地理分布、生态特点及其与植被分布的关系。中国针茅属有32种1亚种及4变种,据该属各个种所处环境中的气候和土壤等因素的变化,不同种的分布也各异。属的分布区的类型属于吴征镒(1979)的中国植物区系分区的泛北极植物区中的6个植物亚区,即亚洲荒漠植物亚区,欧、亚森林植物亚区,青藏高原植物亚区,中国-喜马拉雅植物亚区,欧、亚草原植物亚区及中国-日本森林植物亚区。     

Population structure and conservation genetics of wild rice Oryza rufipogon (Poaceae): a region-wide perspective from microsatellite variation

Oryza rufipogon Griff. is the most agriculturally important but seriously endangered wild rice species. To better estimate how genetic structure can be used to obtained a conservation perspective of the species, genetic variability at six polymorphic microsatellite DNA loci was examined. High levels of genetic variability were detected at six loci in 1245 individuals of 47 natural populations covering most of the species' range in China (overall RS = 3.0740, HO = 0.2290, HS = 0.6700). Partitioning of genetic variability (FST = 0.246) showed that most microsatellite variation was distributed within populations. Significant departures from Hardy-Weinberg expectations and very strong linkage disequilibrium indicate a high degree of inbreeding in the species and severe subdivision within populations. A mean Nm value of 0.7662 suggested a limited gene flow among the assayed populations. Our study suggests that conservation and restoration genetics should focus in particular on the maintenance of historically significant processes such as high levels of outbreeding and gene flow and large effective population size in the species.     

濒危植物长叶榧群体遗传多样性的RAPD分析

借助随机扩增多态DNA方法,分析了中国特有的濒危植物长叶榧的遗传多样性和遗传分化．结果表明：12个随机引物在9个长叶榧自然群体180个样品中可检测到180个可重复位点,其中多态位点119个．长叶榧物种水平的遗传多样性较高,多态位点百分率（P）为66．11％,Shannon信息指数（,）为0．3087,Nei指数（h）为0．2015;而群体水平的遗传多样性较低,P、I和h分别平均为23．76％、0．1221和0．0813．AMOVA分子变异显示,42．57％变异来源于群体内,57．43％变异来源于群体间,群体间的遗传分化系数（Gst）为0．5965,群体间的遗传分化程度高．长叶榧群体间的基因流很低,为0．3382．瓶颈效应、群体隔离和群体间基因流低等因素都加剧了长叶榧群体间的遗传分化．9个长叶榧群体间的平均遗传距离为0．1630．通过UPGMA进行聚类,可将9个长叶榧群体分为浙江和福建两大类群．建议在迁地保护时应尽量避免在群体之间实施种质迁移．     

Evolutionary history of Scinax treefrogs on land‐bridge islands in south‐eastern Brazil

Aim We investigated how Pleistocene refugia and recent (c. 12,000 years ago) sea level incursions shaped genetic differentiation in mainland and island populations of the Scinax perpusillus treefrog group. Location Brazilian Atlantic Forest, São Paulo state, south‐eastern Brazil. Methods Using mitochondrial and microsatellite loci, we examined population structure and genetic diversity in three species from the S. perpusillus group, sampled from three land‐bridge islands and five mainland populations, in order to understand the roles of Pleistocene forest fragmentation and sea level incursions on genetic differentiation. We calculated metrics of relatedness and genetic diversity to assess whether island populations exhibit signatures of genetic drift and isolation. Two of the three island populations in this study have previously been described as new species based on a combination of distinct morphological and behavioural characters, thus we used the molecular datasets to determine whether phenotypic change is consistent with genetic differentiation. Results Our analyses recovered three distinct lineages or demes composed of northern mainland São Paulo populations, southern mainland São Paulo populations, and one divergent island population. The two remaining island populations clustered with samples from adjacent mainland populations. Estimates of allelic richness were significantly lower, and estimates of relatedness were significantly higher, in island populations relative to their mainland counterparts. Main conclusions Fine‐scale genetic structure across mainland populations indicates the possible existence of local refugia within São Paulo state, underscoring the small geographic scale at which populations diverge in this species‐rich region of the Atlantic Coastal Forest. Variation in genetic signatures across the three islands indicates that the populations experienced different demographic processes after marine incursions fragmented the distribution of the S. perpusillus group. Genetic signatures of inbreeding and drift in some island populations indicate that small population sizes, coupled with strong ecological selection, may be important evolutionary forces driving speciation on land‐bridge islands.     

When North and South don’t mix: genetic connectivity of a recently endangered oceanic cycad,Cycas micronesica,in Guam using EST‐microsatellites

Subject to environmental changes and recurrent isolation in the last ca. 250 Ma, cycads are often described as relicts of a previously common lineage, with populations characterized by low genetic variation and restricted gene flow. We found that on the island of Guam, the endemic Cycas micronesica has most of the genetic variation of 14 EST‐microsatellites distributed within each of 18 genetic populations, from 24 original sampling sites. There were high levels of genetic variation in terms of total number of alleles and private alleles, and moderate levels of inbreeding. Restricted but ongoing gene flow among populations within Guam reveals a genetic mosaic, probably more typical of cycads than previously assumed. Contiguous cycad populations in the north of Guam had higher self‐recruitment rates compared to fragmented populations in the south, with no substantial connection between them except for one population. Guam’s genetic mosaic may be explained by the influence of forest continuity, seed size, edaphic differences, and human transport of cycads. Also important are the extent of synchrony among flushes of reproductive female seed‐bearing sporophylls and restricted pollen movement by an obligate mutualist and generalist insects. An NADH EST‐locus under positive selection may reflect pressure from edaphic differences across Guam. This and three other loci are ideal candidates for ecological genomic studies. Given this species’ vulnerability due to the recent introduction of the cycad aulacaspis scale, we also identify priority populations for ex situ conservation, and provide a genetic baseline for understanding the effects of invasive species on cycads in the Western Pacific, and islands in general.     

Population structuring of the ubiquitous stingless bee Tetragonisca angustula in southern Brazil as revealed by microsatellite and mitochondrial markers

Tetragonisca angustula is one of the most widespread stingless bees in the Neotropics. This species swarms frequently and is extremely successful in urban environments. In addition, it is one of the most popular stingless bee species for beekeeping in Latin America, so nest transportation and trading is common. Nest transportation can change the genetic structure of the host population, reducing inbreeding and increasing homogenization. Here, we evaluate the genetic structure of 17 geographic populations of T. angustula in southern Brazil to quantify the level of genetic differentiation between populations. Analyses were conducted on partially sequenced mitochondrial genes and 11 microsatellite loci of 1002 workers from 457 sites distributed on the mainland and on 3 islands. Our results show that T. angustula populations are highly differentiated as demonstrated by mitochondrial DNA (mtDNA) and microsatellite markers. Of 73 haplotypes, 67 were population‐specific. MtDNA diversity was low in 9 populations but microsatellite diversity was moderate to high in all populations. Microsatellite data suggest 10 genetic clusters and low level of gene flow throughout the studied area. However, physical barriers, such as rivers and mountain ranges, or the presence or absence of forest appear to be unrelated to population clusters. Factors such as low dispersal, different ecological conditions, and isolation by distance are most likely shaping the population structure of this species. Thus far, nest transportation has not influenced the general population structure in the studied area. However, due to the genetic structure we found, we recommend that nest transportation should only occur within and between populations that are genetically similar.     

Microsatellite variation and assessment of genetic structure in tea tree (Melaleuca alternifolia– Myrtaceae)

Analysis of five microsatellite loci in 500 Melaleuca alternifolia individuals produced 98 alleles that were useful for population genetic studies. Considerable levels of observed heterozygosity were recorded (HO = 0.724), with approximately 90% of the variability being detected within populations. A low level of selfing (14%) was suggested to be the principal cause of excess homozygosity in a number of populations (overall FIS = 0.073). This study showed low levels of inbreeding in certain populations as well as a significant isolation-by-distance model. Only two groups of populations (Queensland and New South Wales) constituted different genetic provenances as a result of geographical isolation. The M. alternifolia data suggest that microsatellite loci did not always arise by a stepwise mutation process but that larger jumps in allele size may be involved in their evolution.