Integrating geographic ranges across temporal scales

Geographic ranges are a fundamental unit of biogeography and macroecology. Increasingly, paleontologists and ecologists alike are reconstructing geographic ranges of species from fossils, in order to understand the long-term processes governing biogeographic and macroevolutionary patterns. As these reconstructions have become increasingly common, uncertainty has arisen over the equivalency of paleo-ranges and modern ranges. Here, we argue geographic ranges are time-averaged at all temporal scales, and reflect the biotic and abiotic processes operating across the equivalent range of time and space scales. This conceptual framework integrates the study of geographic ranges reconstructed using modern and ancient data, and highlights the potential for ranges to illuminate processes responsible for diversity patterns over intervals spanning days to tens of millions of years of Earth history.

Population genomic signatures of the oriental fruit moth related to the Pleistocene climates

The Quaternary climatic oscillations are expected to have had strong impacts on the evolution of species. Although legacies of the Quaternary climates on population processes have been widely identified in diverse groups of species, adaptive genetic changes shaped during the Quaternary have been harder to decipher. Here, we assembled a chromosome-level genome of the oriental fruit moth and compared genomic variation among refugial and colonized populations of this species that diverged in the Pleistocene. High genomic diversity was maintained in refugial populations. Demographic analysis showed that the effective population size of refugial populations declined during the penultimate glacial maximum (PGM) but remained stable during the last glacial maximum (LGM), indicating a strong impact of the PGM rather than the LGM on this pest species. Genome scans identified one chromosomal inversion and a mutation of the circadian gene Clk on the neo-Z chromosome potentially related to the endemicity of a refugial population. In the colonized populations, genes in pathways of energy metabolism and wing development showed signatures of selection. These different genomic signatures of refugial and colonized populations point to multiple impacts of Quaternary climates on adaptation in an extant species.

Mating system shifts a species' range

Understanding the ecological and evolutionary mechanisms that shape a species' range is an important goal in evolutionary biology. Evidence indicates that mating system is an effective predictor of the global range of native species or naturalized alien plants, but the mechanisms underlying this predictability are not elaborated. Here, we develop a theoretical model to account for the ranges of plants under different mating systems based on migration-selection processes (an idea proposed by Haldane). The model includes alternation of gametophyte and sporophyte generations in one life cycle and the dispersal of haploid pollen and diploid seeds as vectors for gene flow. We show that the interaction between selfing rates and gametophytic selection determines the role of mating system in shaping a species' range. Selfing restricts the species' range under gametophytic selection in nonrandom mating systems, but expands the species' range under the absence of gametophytic selection in any mating system. Gametophytic selection slightly restricts the species' range in random mating. Both logarithmic and logistic models of population demography yield similar conclusions in the case of fixed or evolving genetic variance. The theory also helps to explain a broader relationship between mating system and range size following biological invasion or plant naturalization.

Inventory of Lowland-Breeding Birds on the Alaska Peninsula

We conducted the first systematic inventory of birds in the lowlands (areas ≤100 m above sea level) of the Alaska Peninsula during summers of 2004–2007 to determine their breeding distributions and habitat associations in this remote region. Using a stratified random survey design, we allocated sample plots by elevation and land cover with a preference for wetland cover types used by shorebirds, a group of particular interest to land managers. We surveyed birds during 10-min counts at 792 points across 52, 5 km × 5 km sample plots distributed from south of the Naknek River (58.70°N,157.00°W) to north of Port Moller (56.00°N,160.52°W). We detected 95 bird species including 19 species of shorebirds and 34 species (36% of total) considered at the time to be of conservation concern for the land managers in the region. The most numerous shorebirds on point counts were dunlin Calidris alpina, short-billed dowitcher Limnodromus griseus, and Wilson's snipe Gallinago delicata. We found the breeding-season endemic marbled godwit Limosa fedoa beringiae at 20 plots within a 3,000-km2 area from north of Ugashik Bay to just north of Port Heiden and east to the headwaters of the Dog Salmon and Ugashik rivers. The most abundant passerines on point counts were American tree sparrow Spizelloides arborea, Lapland longspur Calcarius lapponicus, and savannah sparrow Passerculus sandwichensis. Sandhill crane Antigone canadensis, glaucous-winged gull Larus glaucescens, and greater scaup Aythya marila were also relatively abundant. We categorized habitat associations for 30 common species and found that lowland herbaceous vegetation supported wetland-focused species including sandhill crane, marbled godwit, short-billed dowitcher, and dunlin; whereas, dwarf shrub-ericaceous vegetation supported tundra-associated species such as willow ptarmigan Lagopus lagopus, rock sandpiper Calidris ptilocnemis, and American pipit Anthus rubescens. Tall shrub vegetation was important to several species of warblers and sparrows, as well as one species of shorebird (greater yellowlegs Tringa melanoleuca). We found that point counts augmented with incidental observations provided an almost complete inventory of lowland-breeding species on the study area. These data form a baseline to monitor any future changes in bird distribution and abundance on the Alaska Peninsula.

Inferring ecological explanations for biogeographic boundaries of parapatric Asian mountain frogs

Background

Identifying and understanding the mechanisms that shape barriers to dispersal and resulting biogeographic boundaries has been a longstanding, yet challenging, goal in ecology, evolution and biogeography. Characterized by stable, adjacent ranges, without any intervening physical barriers, and limited, if any, range overlap in a narrow contact zone, parapatric species are an interesting system for studying biogeographic boundaries. The geographic ranges of two parapatric frog species, Feirana quadranus and F. taihangnica, meet in a contact zone within the Qinling Mountains, an important watershed for East Asia. To identify possible ecological determinants of the parapatric range boundaries for two closely related frog species, we quantified the extent of their niche differentiation in both geographical and environmental space combining ecological niche models with an ordination technique. We tested two alternative null hypotheses (sharp environmental gradients versus a ribbon of unsuitable habitat dividing two highly suitable regions) for biogeographic boundaries, against the null expectation that environmental variation across a given boundary is no greater than expected by chance.

Results

We found that the niches of these two parapatric species are more similar than expected by chance, but not equivalent. No sharp environmental gradient was found, while a ribbon of unsuitable habitat did act as a barrier for F. quadranus, but not for F. taihangnica.

Conclusions

Integrating our findings with historical biogeographic information, our results suggest that at a contact zone, environmental tolerance restricted F. quadranus from dispersing further north, while interspecific competition most likely prevented the southward expansion of F. taihangnica. This study highlights the importance of both climate and competition in exploring ecological explanations for parapatric range boundaries between ecologically similar frog species, in particular under the effects of changing climate.

Electronic supplementary material

The online version of this article (10.1186/s12898-018-0160-5) contains supplementary material, which is available to authorized users.

Time-restricted flight ability influences dispersal and colonization rates in a group of freshwater beetles

Variation in the ability to fly or not is a key mechanism for differences in local species occurrences. It is increasingly acknowledged that physiological or behavioral mechanisms rather than morphological differences may drive flight abilities. However, our knowledge on the seasonal variability and stressors creating nonmorphological differences in flight abilities and how it scales to local and regional occurrences is very limited particularly for small, short‐lived species such as insects. Here, we examine how flight ability might vary across seasons and between two closely related genera of freshwater beetles with similar geographical ranges, life histories, and dispersal‐related morphology. By combining flight experiments of >1,100 specimens with colonization rates in a metacommunity of 54 ponds in northern and eastern Europe, we have analyzed the relationship between flight ability and spatio‐environmental distribution of the study genera. We find profound differences in flight ability between the two study genera across seasons. High flight ability for Acilius (97% of the tested individuals flew during the experiments) and low for Graphoderus (14%) corresponded to the different colonization rates of newly created ponds. Within a 5‐year period, 81 and 31% of the study ponds were colonized by Acilius and Graphoderus, respectively. While Acilius dispersed throughout the season, flight activity in Graphoderus was restricted to stressed situations immediately after the emergence of adults. Regional colonization ability of Acilius was independent of spatial connectivity and mass effect from propagule sources. In contrast, Graphoderus species were closely related to high connectivity between ponds in the landscape. Our data suggest that different dispersal potential can account for different local occurrences of Acilius and Graphoderus. In general, our findings provide some of the first insights into the understanding of seasonal restrictions in flight patterns of aquatic beetles and their consequences for species distributions.

Impacts of biogeographic history and marginal population genetics on species range limits: a case study of Liriodendron chinense

Species ranges are influenced by past climate oscillations, geographical constraints, and adaptive potential to colonize novel habitats at range limits. This study used Liriodendron chinense, an important temperate Asian tree species, as a model system to evaluate the roles of biogeographic history and marginal population genetics in determining range limits. We examined the demographic history and genetic diversity of 29 L. chinense populations using both chloroplast and nuclear microsatellite loci. Significant phylogeographic structure was recovered with haplotype clusters coinciding with major mountain regions. Long-term demographical stability was suggested by mismatch distribution analyses, neutrality tests, and ecological niche models (ENM) and suggested the existence of LGM refuges within mountain regions. Differences in genetic diversity between central and marginal populations were not significant for either genomic region. However, asymmetrical gene flow was inferred from central populations to marginal populations, which could potentially limit range adaptation and expansion of L. chinense.

Edging along a Warming Coast: A Range Extension for a Common Sandy Beach Crab

Determining the position of range edges is the first step in developing an understanding of the ecological and evolutionary dynamics in play as species’ ranges shift in response to climate change. Here, we study the leading (poleward) range edge of Ocypode cordimanus, a ghost crab that is common along the central to northern east coast of Australia. Our study establishes the poleward range edge of adults of this species to be at Merimbula (36.90°S, 149.93°E), 270 km (along the coast) south of the previous southernmost museum record. We also establish that dispersal of pelagic larvae results in recruitment to beaches 248 km (along the coast; 0.9° of latitude) beyond the adult range edge we have documented here. Although we cannot conclusively demonstrate that the leading range edge for this species has moved polewards in response to climate change, this range edge does fall within a “hotspot” of ocean warming, where surface isotherms are moving southwards along the coast at 20–50 km.decade^-1; coastal air temperatures in the region are also warming. If these patterns persist, future range extensions could be anticipated. On the basis of their ecology, allied with their occupancy of ocean beaches, which are home to taxa that are particularly amenable to climate-change studies, we propose that ghost crabs like O. cordimanus represent ideal model organisms with which to study ecological and evolutionary processes associated with climate change. The fact that “hotspots” of ocean warming on four other continents correspond with poleward range edges of ghost crab species suggests that results of hypothesis tests could be generalized, yielding excellent opportunities to rapidly progress knowledge in this field.

Ecological genetics of range size variation in Boechera spp. (Brassicaceae)

Many taxonomic groups contain both rare and widespread species, which indicates that range size can evolve quickly. Many studies have compared molecular genetic diversity, plasticity, or phenotypic traits between rare and widespread species; however, a suite of genetic attributes that unites rare species remains elusive. Here, using two rare and two widespread Boechera (Brassicaceae) species, we conduct a simultaneous comparison of quantitative trait diversity, genetic diversity, and population structure among species with highly divergent range sizes. Consistent with previous studies, we do not find strong associations between range size and within-population genetic diversity. In contrast, we find that both the degree of phenotypic plasticity and quantitative trait structure (Q ST) were positively correlated with range size. We also found higher F ST: Q ST ratios in rare species, indicative of either a greater response to stabilizing selection or a lack of additive genetic variation. While widespread species occupy more ecological and climactic space and have diverged at both traits and markers, rare species display constrained levels of population differentiation and phenotypic plasticity. Combined, our results provide evidence for a specialization-generalization trade-off across three orders of magnitude of range size variation in the ecological model genus, Boechera.

Role of sex and migration in adaptation to sink environments

Understanding the effects of sex and migration on adaptation to novel environments remains a key problem in evolutionary biology. Using a single-cell alga Chlamydomonas reinhardtii, we investigated how sex and migration affected rates of evolutionary rescue in a sink environment, and subsequent changes in fitness following evolutionary rescue. We show that sex and migration affect both the rate of evolutionary rescue and subsequent adaptation. However, their combined effects change as the populations adapt to a sink habitat. Both sex and migration independently increased rates of evolutionary rescue, but the effect of sex on subsequent fitness improvements, following initial rescue, changed with migration, as sex was beneficial in the absence of migration but constraining adaptation when combined with migration. These results suggest that sex and migration are beneficial during the initial stages of adaptation, but can become detrimental as the population adapts to its environment.

Thermal tolerance breadths among groundwater crustaceans living in a thermally constant environment

Abstract: The climate variability hypothesis assumes that the thermal tolerance breadth of a species is primarily determined by temperature variations experienced in its environment. If so, aquatic invertebrates living in thermally-buffered environments would be expected to exhibit narrow thermal tolerance breadths (stenothermy). We tested this prediction by studying the thermal physiology of 3 isopods (Asellidae, Proasellus) colonizing groundwater habitats characterized by annual amplitude of temperature less than 1°C. The species responses to temperature variation were assessed in the laboratory using five physiological variables: survival, locomotor activity, aerobic respiration, immune defense and concentrations of total free amino acids and sugars. The three species exhibited contrasted thermal physiologies although all variables were not equally informative. In accordance with the climate variability hypothesis, two species were extremely sensitive even to moderate changes in temperature (2°C) below and above their habitat temperature. In contrast, the third species exhibited a surprisingly high thermal tolerance breadth (11°C). Differences in response to temperature variation among Proasellus species indicated that their thermal physiology was not solely shaped by the current temperature seasonality in their natural habitats. More particularly, recent gene flow among populations living in thermally constant yet contrasted habitats might explain the occurrence of eurytherm species in thermally buffered environments.

Phylogeography and species biogeography of montane Great Basin stoneflies

Sky islands are ideal systems for determining the effects of climatic oscillations on species distributions and genetic structure. Our study focused on montane stonefly populations in the Great Basin of western North America. We used niche-based distribution modelling, phylogeography and traditional species-based biogeography to test several hypotheses as follows: (i) genetic differentiation among Doroneuria baumanni populations will be independent of hydrologic connectivity (headwater model); (ii) Sky islands were colonized when habitat was more continuous and populations likely experienced multiple expansions and contractions; (iii) Colonization events were coincident with the late Pleistocene and Holocene; and (iv) Shared topography and climate history will result in concordant patterns of genetic differentiation in D. baumanni and occurrences of 32 stonefly species across the region. Overall, Φ(ST) 's and coalescent-based estimates of migration were consistent with the headwater model. Maximum likelihood and Bayesian gene trees identified three major nonoverlapping east-west clades. Distribution modelling indicated more suitable habitat in the Great Basin during the Last Glacial Maximum than at present, but none during the last interglacial period. Demographic analyses showed evidence of population expansion in one of the three major east-west clades. Intra-clade divergence times (60,000-183,000ybp) were well within the late Pleistocene while among-clade divergence times (499.000-719,000ybp) were deeper. Genetic differentiation in D. baumanni and distributions of stonefly species were significantly concordant. These results imply that climatic oscillations have played major roles in shaping the genetic structure and distributions of Great Basin stoneflies, but that divergence among clades occurred much earlier than our late Pleistocence/early Holocene predictions.

Geographic location and phylogeny are the main determinants of the size of the geographical range in aquatic beetles

Background

Why some species are widespread while others are very restricted geographically is one of the most basic questions in biology, although it remains largely unanswered. This is particularly the case for groups of closely related species, which often display large differences in the size of the geographical range despite sharing many other factors due to their common phylogenetic inheritance. We used ten lineages of aquatic Coleoptera from the western Palearctic to test in a comparative framework a broad set of possible determinants of range size: species' age, differences in ecological tolerance, dispersal ability and geographic location.

Results

When all factors were combined in multiple regression models between 60-98% of the variance was explained by geographic location and phylogenetic signal. Maximum latitudinal and longitudinal limits were positively correlated with range size, with species at the most northern latitudes and eastern longitudes displaying the largest ranges. In lineages with lotic and lentic species, the lentic (better dispersers) display larger distributional ranges than the lotic species (worse dispersers). The size of the geographical range was also positively correlated with the extent of the biomes in which the species is found, but we did not find evidence of a clear relationship between range size and age of the species.

Conclusions

Our findings show that range size of a species is shaped by an interplay of geographic and ecological factors, with a phylogenetic component affecting both of them. The understanding of the factors that determine the size and geographical location of the distributional range of species is fundamental to the study of the origin and assemblage of the current biota. Our results show that for this purpose the most relevant data may be the phylogenetic history of the species and its geographical location.