Is realised connectivity among populations of aquatic fauna predictable from potential connectivity?

1. Effective management of aquatic fauna requires knowledge of the ways in which populations in different catchments and sub‐catchments are connected. A powerful way to estimate this is using genetic markers, which provide information on the average amount of genetic connectivity among populations over generations. Although many studies of genetic connectivity have appeared in the literature, there are innumerable species that have not been studied. 2. This study explores whether it is possible to make broad generalisations about population connectivity, based on readily available information in the form of species life history and architecture of the aquatic habitat. 3. A number of models have been proposed to explain the pattern of connectivity shown by aquatic species with different life‐history characteristics, for example, the stream hierarchy model, Isolation by Distance, the Death Valley Model, the headwater model and panmixia. 4. In this study, we propose a dichotomous key to assign species to different models of potential connectivity. The key is based on a few very simple questions about the life history of the species and the geographical arrangement of study sites. We then assessed the performance of the key with 109 data sets of Australian fish and macroinvertebrates, using genetic data to provide an estimate of realised connectivity. 5. The realised connectivity fitted the proposed potential connectivity model in over 70% of cases, and we suggest this might be a useful initial approach for managers where empirical data are lacking.     

Is there any genetic differentiation among populations of Piptochaetium napostaense (Speg.) Hack (Poaceae) with different grazing histories?

Native populations of perennial grasses subjected to heavy grazing are typically shorter and more prostrate than ungrazed or lightly defoliated ones. However, it is often difficult to find out whether the morphological modifications are the result of genetic differentiation or phenotypic plasticity. Piptochaetium napostaense (Speg.) Hack. is a native perennial cool-season palatable grass with a dwarf form abundant in the areas subjected to heavy grazing. In this study, we tried to determine whether the populations with different grazing histories are genetically differentiated. We considered three different grazing conditions: enclosure (prevented from grazing during 20 years), livestock grazing, and burrow (heavily grazed by cattle and a wild rodent herbivore, the vizcacha). Isozyme analyses were carried out in order to assess the genetic variability of the populations under study. We further studied the progeny of plants with different grazing histories to determine whether the morphological differences are transmitted to the next generation. Seedlings obtained from seeds belonging to enclosure and burrow were grown in the greenhouse and their vegetative and reproductive response under different water and nutrient availability levels were recorded. From the isozymes analyses we found low levels of genetic variation in the populations studied, with an average of 20.5% polymorphic loci, 1.2 alleles per locus and 0.015 mean expected heterozygosity. From the total genetic diversity, only 1.4% was due to differences among population. In addition, either enclosure or burrow populations had the same growth and reproductive response over treatments differing in water and nutrient levels. The morphological differentiation among plants with different grazing histories appears to be the outcome of a phenotypically plastic response of adapted genotypes.     

Can we bring Madagascar's critically endangered palms back from the brink? Genetics,ecology and conservation of the critically endangered palm Beccariophoenix madagascariensis

Madagascar has a highly distinctive flora and is one of the world biodiversity hot spots. There are more than 170 species of palms, the majority of which are vulnerable, endangered or critically endangered endemics. Palms are utilized for many human uses, many of which lead to plant death or seed harvesting. Combined with reduced populations resulting from extensive forest clearing, those species which are harvested from the wild are under additional threat of extinction. Species recovery programmes have the potential to save some of the most iconic species before it is too late. This study documented the current known populations of the critically endangered palm Beccariophoenix madagascariensis, a species utilized for both local and international purposes. The study specifically investigated the genetic diversity and inbreeding within populations and the potential differentiation between populations and with the newly described species B. alfredii . We found that despite critically small population sizes there was considerable genetic diversity within populations. We also found that ecologically and or geographically distinct populations were genetically distinct. Populations within 3 km of each other exhibited considerable gene flow, probably owing to seed dispersal. The populations were inbred but reproductive viability had been maintained. Conservation and recovery options are discussed. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 589–608.     

Limited genetic diversity and high differentiation among the remnant adder (Vipera berus) populations in the Swiss and French Jura Mountains

Although the adder (Vipera berus) has a large distribution area, this species is particularly threatened in Western Europe due to high habitat fragmentation and human persecution. We developed 13 new microsatellite markers in order to evaluate population structure and genetic diversity in the Swiss and French Jura Mountains, where the species is limited to only a few scattered populations. We found that V. berus exhibits a considerable genetic differentiation among populations (global F_ST = 0.269), even if these are not geographically isolated. Moreover, the genetic diversity within populations in the Jura Mountains and in the less perturbed Swiss Alps is significantly lower than in other French populations, possibly due to post-glacial recolonisation processes. Finally, in order to minimize losses of genetic diversities within isolated populations, suggestions for the conservation of this species in fragmented habitats are proposed.     

Is the genetic structure of Gran Chaco populations unique? Interregional perspectives on native South American mitochondrial DNA variation

This study reevaluates the hypothesis in Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203) that Gran Chaco peoples demonstrate a unique pattern of genetic diversity due to a distinct regional population history. Specifically, they found populations in the central part of the Gran Chaco, or Central Chaco, to have higher within- and lower between-population mitochondrial DNA (mtDNA) haplogroup frequency variation compared to populations in other South American regions. To test this hypothesis of regional uniqueness, we applied analytical and simulation methods to mtDNA first hypervariable (HVI) region sequence data from a broad set of comparative South and Central American population samples. Contrary to the results of Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203), we found that the Gran Chaco's regional within-population diversity is about average among regions, and populations are highly differentiated from each other. When we limited the scale of analysis to the Central Chaco, a more localized subregion of the Gran Chaco, our results fell more in line with the original findings of Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203). Still, we conclude that neither the Gran Chaco regional pattern, nor the Central Chaco subregional pattern, is unique within South America. Nonetheless, the Central Chaco pattern accords well with the area's history, including pre-European contact lifeways and the documented historical use of the area as an interregional crossroads. However, we cannot exclude post-European contact disruption of traditional mating networks as an equally plausible explanation for the observed diversity pattern. Finally, these results additionally inform broader models of South American genetic diversity. While other researchers proposed an east-west continental division in patterns of genetic variation (e.g., Fuselli et al. 2003 Mol. Biol. Evol. 20:1682-1691), we found that in the geographically intermediate Central Chaco, a strict east-west divide in genetic variation breaks down. We suggest that future genetic characterizations of the continent, and subsequent interpretations of evolutionary history, involve a broad regional sampling of South American populations.     

Is there really natural selection affecting the l frequencies (long hair) in the Brazilian cat populations?

The scientific literature on cat genetics contains a presumed typical example of natural selection affecting l frequencies (long hair) in 16 Brazilian cat populations. It has been observed that the hotter and more tropical the climate in Brazil, the lower the values of l frequencies in the cat populations. Nevertheless, this study of some new cat populations in Latin America showed that all of them, independent of the climate, had high or very high l frequencies. l postulate that an alternative migrational-historical hypothesis exists that explains the correlation between the l frequencies and climate characteristics (which are correlated with the latitude) without using natural selection explanations concerning the appearance of the l allele in Brazil.     

Bertilia — A new monotypic genus in the Senecioneae (Asteraceae) from South Africa

The unusual disjunct distribution of the yellow-flowered, radiate, Northern Cape endemic Emilia hantamensis J.C.Manning & Goldblatt, relative to the other Emilia species in southern Africa, prompted investigation into its phylogenetic position and relationships. Phylogenies based on the ITS and trnL–trnF regions reveal that it is not a member of the genus Emilia but belongs in a well-supported clade with Bolandia, a genus comprising five species mainly from the Western and Northern Cape, and the monotypic genera Stilpnogyne and Mesogramma. It is placed sister to Bolandia and its cypselas match those of Bolandia in shape, colour and indumentum, except for a distinct ridge of hairs on the inner rib of the ray cypselas. It is further distinguished from Bolandia by its annual habit and conical disc floret style apices and obtuse to rounded ray floret style apices. It is recognised and described here as a new monotypic genus, Bertilia Cron with the single species B. hantamensis (J.C.Manning & Goldblatt) Cron.     

Trace elements in otoliths of the two‐banded bream from a coastal region in the south‐west Mediterranean: are there differences among locations?

There were no significant differences in otolith chemistry (Li, Mn, Sr, Cd, Ba) of Diplodus vulgaris between sites (distances >100 m) and few differences among locations (distance >10 km) along the south-west coast of Spain. Multivariate analysis of otolith chemistry detected a difference among locations, but a posteriori comparisons could not detect which locations differed. This is one of the few studies to show little variation in otolith chemistry among locations. Of the studies reviewed, <10% showed non-significant differences. It is suggested that the region of the Mediterranean where this study was conducted may be relatively homogeneous in comparison to estuarine and coastal regions where many of the other studies have been conducted.     

Is there a correlation between abundance and environmental suitability derived from ecological niche modelling? A meta‐analysis

It is thought that species abundance is correlated with environmental suitability and that environmental variables, scale, and type of model fitting can confound this relationship. We performed a meta‐analysis to 1) test whether species abundance is positively correlated with environmental suitability derived from correlative ecological niche models (ENM), 2) test whether studies encompassing large areas within a species range (> 50%) exhibited higher AS correlations than studies encompassing small areas within a species range (< 50%), 3) assess which modelling method provided higher AS correlation, and 4) compare strength of the AS relationship between studies using only climatic variables and those that used both climatic and other environmental variables to derive suitability. We used correlation coefficients to measure the relationship between abundance and environmental suitability derived from ENM. Each correlation coefficient was considered an effect size in a random‐effects multivariate meta‐analysis. In all cases we found a significantly positive relationship between abundance and suitability. This relationship was consistent regardless of scale of study, ENM method, or set of variables used to derive suitability. There was no difference in strength of correlation between studies focusing on large or small areas within a species’ range or among ENM methods. Studies using other variables in combination with climate exhibited higher AS correlations than studies using only climatic variables. We conclude that occurrence data can be a reasonable proxy for abundance, especially for vertebrates, and the use of local variables increases the strength of the AS relationship. Use of ENMs can significantly decrease survey costs and allow the study of large‐scale abundance patterns using less information. Including only climatic variables in ENM may confound the relationship between abundance and suitability when compared to studies including variables taken locally. However, modelers and conservationists must be aware that high environmental suitability does not always indicate high abundance.     

Molecular differentiation within and among island populations of the endemic plant Scalesia affinis (Asteraceae) from the Galápagos Islands

Molecular variance was estimated in seven populations of the endemic species Scalesia affinis within and among islands of the Galapagos. The analysis, based on 157 polymorphic AFLP markers, revealed a high differentiation among populations, of which most was partitioned among islands. In addition, the information content of AFLP markers was tested with sets of discriminant analyses based on different numbers of AFLP markers. This indicated that the markers were highly informative in discriminating the populations. Although one of four populations from the island Isabela was sampled from a volcano 100 km away from the remaining populations, this population resembled the others on Isabela. The partitioning of molecular variance (AFLP) resulted in two unities, one consisting of populations from Isabela and one of populations from Santa Cruz and Floreana. The differentiation in two chloroplast microsatellites was higher than for AFLP markers and equally partitioned among populations within islands as among islands. Thus, gene flow via fruits within islands is as limited as among islands. The lower differentiation within islands in the nuclear AFLP markers may thus indicate that gene flow within islands is mostly accounted for by pollen transfer. S. affinis is the only species in the genus that is not listed in 2000 IUCN Red List of Threatened Species. However, due to prominent grazing and land exploitation, some populations have recently been reduced markedly, which was reflected in lower diversity. As inbreeding depression is present in the species, the rapid bottlenecks are threats to the populations.     

Are there morphological and life‐history traits under climate‐dependent differential selection in S Tunesian Diplotaxis harra (Forssk.) Boiss. (Brassicaceae) populations?

Adaptation of morphological, physiological, or life‐history traits of a plant species to heterogeneous habitats through the process of natural selection is a paramount process in evolutionary biology. We have used a population genomic approach to disentangle selection‐based and demography‐based variation in morphological and life‐history traits in the crucifer Diplotaxis harra (Forssk.) Boiss. (Brassicaceae) encountered in populations along aridity gradients in S Tunisia. We have genotyped 182 individuals from 12 populations of the species ranging from coastal to semidesert habitats using amplified fragment length polymorphism (AFLP) fingerprinting and assessed a range of morphological and life‐history traits from their progeny cultivated under common‐garden conditions. Application of three different statistical approaches for searching AFLP loci under selection allowed us to characterize candidate loci, for which their association with the traits assessed was tested for statistical significance and correlation with climate data. As a key result of this study, we find that only the shape of cauline leaves seems to be under differential selection along the aridity gradient in S Tunisian populations of Diplotaxis harra, while for all other traits studied neutral biogeographical and/or random factors could not be excluded as explanation for the variation observed. The counter‐intuitive finding that plants from populations with more arid habitats produce broader leaves under optimal conditions of cultivation than those from more mesic habitats is interpreted as being ascribable to selection for a higher plasticity in this trait under more unpredictable semidesert conditions compared to the more predictable ones in coastal habitats.     

Sensitivity to stress in the bivalve Macoma balthica from the most northern (Arctic) to the most southern (French) populations: low sensitivity in Arctic populations because of genetic adaptations?

The stress sensitivity, determined in copper exposureexperiments and in survival in air tests, and thegenetic structure, measured by means of isoenzymeelectrophoresis, were assessed in populations of theBaltic clam Macoma balthica (L.) from itssouthern to its northern distribution limit, in orderto test the hypotheses that near the distributionlimit the clams would be more stress sensitive andwould have a lower genetic variability. Thepopulations in west and north Europe show a stronggenetic resemblance. The populations in the sub-ArcticWhite Sea are genetically slightly different, and showa low stress sensitivity. The populations in theArctic Pechora Sea are genetically very distant fromthe other populations, and show the lowest stresssensitivity. Near the southern distribution limit, inagreement with the hypotheses, genetic variability islow and stress sensitivity high. On the other hand, incontrast to expectation, near the northerndistribution limit, in the populations of the PechoraSea, the genetic variability was higher, thus notreduced, and the stress sensitivity was low comparedto all other populations. Yet, it remains a questionif such is due to gradual physiologicalacclimatization (and ongoing differential selection)or to genetic adaptation.     

Is the signal from the mesophyll to the guard cells a vapour‐phase ion?

Previous studies have suggested that the red light and CO₂ responses of stomata are caused by a signal from the mesophyll to the guard cells. Experiments were conducted to test the idea that this signal is a vapour‐phase ion. Stomata in isolated epidermes of Tradescantia pallida were found to respond to air ions created by an electrode that was positioned under the epidermes. Anthocyanins in the epidermes of this species were observed to change colour in response to these air ions, and this change in colour was attributed to changes in pH. A similar change in lower epidermal colour was observed in intact leaves upon illumination and with changes in CO₂ concentration. Based on the change in epidermal colour, the pH of the epidermis was estimated to be approximately 7.0 in darkness and 6.5 in the light. Stomata in isolated epidermes responded to pH when suspended over (but not in contact with) solutions of different pH. We speculate that stomatal responses to CO₂ and light are caused by vapour‐phase ions, possibly hydronium ions that change the pH of the epidermis.     

Is there sex-biased resistance and tolerance in Mediterranean wood mouse (Apodemus sylvaticus) populations facing multiple helminth infections?

Sex-biased parasitism is rarely investigated in relation to host tolerance and resistance, which are two defense strategies hosts can adopt when challenged by parasites. Health or fitness deteriorations in less tolerant individuals with increasing parasite burden would be faster than those in more tolerant ones. Hence, the body condition and reproductive potential of an infected individual host can be considered proxies for tolerance to parasitism. We studied Mediterranean populations of the wood mouse (Apodemus sylvaticus) and its helminth parasites. We assessed their resistance using the phytohemagglutinin test and spleen size, and their tolerance using body condition in males and females and testes mass in males. In order to avoid spurious correlations, we took into account the phylogeographic structure of the Mediterranean wood mouse populations. We used a mixed model adapted from the animal model used in quantitative genetics. While helminth infection did not differ between the two sexes, females and males differed in their measured defenses. Females seem to invest more in immune defense with increasing risk of parasite diversity, but also appear to be potentially more tolerant of parasitic diversity. These results suggest the existence of sexual differences in resistance and tolerance, and that measurements of parasitic loads alone could be insufficient to detect any underlying sexual differences in the two strategies that have evolved in response to multiple parasitic attacks.     

Testing the effect of transient Plio‐Pleistocene barriers in monsoonal Australo‐Papua: did mangrove habitats maintain genetic connectivity in the Black Butcherbird?

Changes in climate and sea level are hypothesized to have promoted the diversification of biota in monsoonal Australia and New Guinea by causing repeated range disjunctions and restricting gene flow between isolated populations. Using a multilocus (one mtDNA locus, five nuclear introns) phylogeographic approach, we test whether populations of the mangrove and rainforest restricted Black Butcherbird (Cracticus quoyi) have diverged across several geographic barriers defined a priori for this region. Phylogeographic structure and estimates of divergence times revealed Plio-Pleistocene divergences and long-term restricted gene flow of populations on either side of four major geographic barriers between and within Australia and New Guinea. Overall, our data are consistent with the hypothesis that mesic-adapted species did not disperse across the open dry woodlands and grasslands that dominated the transient palaeo-landbridges during the Plio-Pleistocene despite the presence of mangrove forests that might have acted as dispersal corridors for mesic-adapted species. Our study offers one of the first multilocus perspectives on the impact of changes in climate and sea level on the population history of widespread species with disjunct ranges in Australia and New Guinea.     

Can gene flow among populations counteract the habitat loss of extremely fragile biotopes? An example from the population genetic structure in Salix daphnoides

Wild river gravel banks (RGB) represent an extremely fragile biotope that is significantly endangered by human activities due to its fragmentation over the past century. The consequences of such processes were studied using the endangered violet willow (Salix daphnoides) at the westernmost foothills of the Carpathian Mountains. We quantified population genetic characteristics for 14 ecologically and demographically characterised populations using simple sequence repeats (SSR) and amplified fragment length polymorphism (AFLP) markers. We found a significant correlation between the biotope, sex, age and genetic structure of the populations. The natural RGB populations revealed high genotypic variability when using SSR markers, in contrast to low genotypic variability of the populations of other biotopes of Cirsium wet meadows (CWM) and Ash-alder forests (AAF) that consisted of one to two clones at each site. High heterozygosity (H _obs?=?0.428–0.532) was similar across all natural (RGB) populations; however, these populations were deficient in heterozygotes (F _IS/ρ _IS?>?0). All RGB populations exhibited moderate to very significant genetic differentiation for microsatellites, despite the fact that the AFLP data showed strong differentiation only between CWM and AAF populations. Division into clusters by Structure confirmed consistent geographic groups for the RGB populations. According to our results, the strong decrease in previously continuous and large natural habitats for the violet willow is slightly counterbalanced by among-population gene flow. However, the survival of natural populations is tightly linked to the presence of river gravel banks and bars. Strict protection of this habitat is therefore essential for the conservation of the species.     

Start codon targeted (SCoT) polymorphism-based genetic relationships and diversity among populations of <Emphasis Type="Italic">Tecomella undulata</Emphasis> (Sm.) Seem—an endangered timber tree of hot arid regions

Tecomella undulata (Sm.) Seem commonly called Rohida or Desert teak (family bignoniaceae) is an important agroforestry tree having an important pharmacological and therapeutic uses. Its distribution is restricted to hot arid regions of India and Pakistan having <150 to 500 mm annual rainfall. Genetic diversity status of this important endangered timber tree species designated state flower of Rajasthan remains unrevealed. Genetic diversity of 21 populations (108 accessions) encompassing yellow, red and orange coloured flower bearing morphotypes collected from all 12 districts of western Rajasthan, India, has been examined using start codon targeted (SCoT) polymorphism for the first time. Fingerprinting with 22 SCoT primers (out of 36 screened) generated 294 amplicons of 100 to 3000 bp size, of which 212 (71.6%) were polymorphic. Amplicon number varied from 4 (SCoT-9) to 24 (SCoT-15) with an average of 13.4 amplicons per primer. Average polymorphism information content (PIC), Nei’s diversity index (H) and Shannon index (I) were 0.54, 0.22 and 0.36, respectively. Dendrogram generated using unweighted pair-group method with arithmetic mean (UPGMA) delineated the 108 accessions into 5 clusters while 2 accessions out grouped. Principal coordinate analysis (PCoA) also revealed similar clustering. High level of genetic differentiation among accessions/populations was attributed to cross pollination and continuous evolution under harsh agro-climatic conditions.     

Low mitochondrial DNA diversity in the endangered Bonelli’s Eagle (Hieraaetus fasciatus) from SW Europe (Iberia) and NW Africa

This study is an initial survey of the genetic diversity and population structure of the endangered Bonelli’s Eagle (Hieraaetus fasciatus) in SW Europe (Iberia) and NW Africa, two locations where the species has undergone a severe decrease in numbers during the last decades. It is also the first study in which the mitochondrial control region (CR) has been used to study the genetic diversity and population structure of this species. Samples were obtained from 72 individuals from Spain, Portugal and Morocco, and a 253-bp fragment of the mitochondrial control region was amplified and sequenced. Only three polymorphisms were present, indicating low nucleotide and haplotype diversity. No evidence of genetic structure was found. Several hypotheses may explain these results, including a possible greater genetic diversity in other regions of the mitochondrial genome or the existence of a presumed ancient bottleneck (last glaciation), possibly followed by a human-induced more recent one (twentieth century).     

Do differences in life‐history traits and the timing of peak mating activity between host‐associated populations of Chilo suppressalis have a genetic basis?

The development of host races, genetically distinct populations of the same species with different hosts, is considered to be the initial stage of ecological speciation. Ecological and biological differences consistent with host race formation have been reported between water‐oat and rice‐associated populations of Chilo suppressalis. In order to confirm whether these differences have a genetic basis, we conducted experiments to determine the extent to which various life‐history traits and the time of peak mating activity of these populations were influenced by the species of host plant larvae were raised on. Individuals from each population were reared for three consecutive generations on either water‐oat fruit pulp or rice seedlings. Descendants of both populations had higher larval survival rates, shorter larval developmental periods, higher pupal weight, and longer adult forewings, when reared on water‐oats than when reared on rice. The time of peak of mating activity differed between the descendants of each population, irrespective of whether they were raised on water‐oats or rice. These results indicate that although some life‐history traits of host‐associated populations of C. suppressalis are influenced by the host plant larvae are raised on, time of peak mating activity is not. Because it is a stable, objective, phenotypic trait, further research on difference in the time of peak mating activity between host‐associated populations of C. suppressalis should be conducted to clarify the mechanism responsible for host race formation in this species.