Comparative phylogeography and the history of endemic vertebrates in the Wet Tropics rainforests of Australia

We examine the effects of historical climate change on vertebrate differentiation in tropical rainforest by comparing phylogeographic patterns in six species of widespread rainforest-restricted herpetofauna from throughout the Wet Tropics of Australia. Qualitative and quantitative comparisons of phylogeographic structure reveal strikingly similar patterns of pre-Pleistocene vicariant population differentiation on either side of a previously identified biogeographic break (variously referred to as the Black Mountain Barrier or Corridor; BMC). While divergence across the BMC antedates the Pleistocene, the impact of Quaternary climate change is apparent in populations on either side of the BMC. Consistent with palaeoclimatological reconstructions for the region, the distribution and degree of mtDNA diversity suggests that populations were fragmented and reduced to multiple refugia during Pleistocene glacial periods, with expansion following Holocene rainforest recovery. This pattern is repeated on both sides of the BMC, but substantial differences in the amount and distribution of mtDNA diversity within species indicate the importance of species-specific ecological characteristics. The historical processes of extinction and (re)colonization revealed by the comparative phylogeographic analysis of mtDNA sequences substantiate earlier suggestions that current regional patterns of species distribution and diversity in the Wet Tropics are largely determined by local extinctions and subsequent recolonization driven by Quaternary climate changes.     

Immigrants and refugees: the importance of dispersal in mediating biotic attrition under climate change

Montane tropical rainforests are critically important areas for global bird diversity, but are projected to be highly vulnerable to contemporary climate change. Upslope shifts of lowland species may partially offset declines in upland species but also result in a process of lowland biotic attrition. This latter process is contingent on the absence of species adapted to novel warm climates, and isolation from pools of potential colonizers. In the Australian Wet Tropics, species distribution modelling has forecast critical declines in suitable environmental area for upland endemic birds, raising the question of the future role of both natural and assisted dispersal in species survival, but information is lacking for important neighbouring rainforest regions. Here we use expanded geographic coverage of data to model the realized distributions of 120 bird species found in north‐eastern Australian rainforest, including species from potential source locations in the north and recipient locations in the south. We reaffirm previous conclusions as to the high vulnerability of this fauna to global warming, and extend the list of species whose suitable environmental area is projected to decrease. However, we find that expansion of suitable area for some species currently restricted to northern rainforests has the potential to offset biotic attrition in lowland forest of the Australian Wet Tropics. By examining contrasting dispersal scenarios, we show that responses to climate change in this region may critically depend on dispersal limitation, as climate change shifts the suitable environmental envelopes of many species south into currently unsuitable habitats. For lowland and northern species, future change in vegetation connectivity across contemporary habitat barriers is likely to be an important mediator of climate change impacts. In contrast, upland species are projected to become increasingly isolated and restricted. Their survival is likely to be more dependent on the viability of assisted migration, and the emergence and persistence of suitable environments at recipient locations.     

Can changes in ant diversity along elevational gradients in tropical and subtropical Australian rainforests be used to detect a signal of past lowland biotic attrition?

Increasing temperatures are predicted to have profound effects on montane ecosystems. In tropical forests, biotic attrition may reduce lowland diversity if losses of species due to upslope range shifts are not matched by influxes of warmer‐adapted species, either because there are none or their dispersal is impeded. Australian rainforests consist of a north–south chain of patches, broken by dry corridors that are barriers to the dispersal of rainforest species. These rainforests have repeatedly contracted and expanded during Quaternary glacial cycles. Many lowland rainforests are expansions since the Last Glacial Maximum and may, therefore, show a signal of historical biotic attrition. We surveyed ants from replicated sites along three rainforest elevational transects in eastern Australia spanning 200 to 1200 m a.s.l. and nearly 14° of latitude. We examined elevational patterns of ant diversity and if there was possible evidence of lowland biotic attrition. Each transect was in a different biogeographic region; the Australian Wet Tropics (16.3°S), the central Queensland coast (21.1°S) and subtropical south‐eastern Queensland (28.1°S). We calculated ant species density (mean species per site) and species richness (estimated number of species by incorporating site‐to‐site species turnover) within elevational bands. Ant species density showed no signal of lowland attrition and was high at low and mid‐elevations and declined only at high elevations at all transects. Similarly, estimated species richness showed no evidence of lowland attrition in the Wet Tropics and subtropical south‐east Queensland; species richness peaked at low elevations and declined monotonically with increasing elevation. Persistence of lowland rainforest refugia in the Wet Tropics during the Last Glacial Maximum and latitudinal range shifts of ants in subtropical rainforests during the Holocene climatic optimum may have counteracted lowland biotic attrition. In central Queensland, however, estimated richness was similar in the lowlands and mid‐elevations, and few ant species were indicative of lower elevations. This may reflect historical biotic attrition due perhaps to a lack of lowland glacial refugia and the isolation of this region by a dry forest barrier to the north.     

Variable responses of skinks to a common history of rainforest fluctuation: concordance between phylogeography and palaeo-distribution models

There is a growing appreciation of impacts of late-Quaternary climate fluctuations on spatial patterns of species and genetic diversity. A major challenge is to understand how and why species respond individualistically to a common history of climate-induced habitat fluctuation. Here, we combine modelling of palaeo-distributions and mitochondrial-DNA phylogeographies to compare spatial patterns of population persistence and isolation across three species of rainforest skinks ( Saproscincus spp.) with varying climatic preferences. Using Akaike Information Criterion model-averaged projections, all three species are predicted to have maintained one or more small populations in the northern Wet Tropics, multiple or larger populations in the central region, and few if any in the south. For the high-elevation species, Saproscincus czechurai , the warm–wet climate of the mid Holocene was most restrictive, whereas for the generalist S. basiliscus and lower-elevation S. tetradactyla, the cool–dry last glacial maximum was most restrictive. As expected, S. czechurai was the most genetically structured species, although relative to modelled distributions, S. basiliscus had surprisingly deep phylogeographical structure among southern rainforest isolates, implying long-term isolation and persistence. For both S. basiliscus and S. tetradactyla, there was high genetic diversity and complex phylogeographical patterns in the central Wet Tropics, reflecting persistence of large, structured populations. A previously identified vicariant barrier separating northern and central regions is supported, and results from these species also emphasize a historical persistence of populations south of another biogeographical break, the Tully Gorge. Overall, the results support the contention that in a topographically heterogeneous landscape, species with broader climatic niches may maintain higher and more structured genetic diversity due to persistence through varying climates.     

Effects of historical forest contraction on the phylogeographic structure of Australo‐Papuan populations of the red‐legged pademelon (Macropodidae: Thylogale stigmatica)

Geographic patterns of genetic variation are strongly influenced by historical changes in species habitats. Whether such patterns are common to co‐distributed taxa may depend on the extent to which species vary in ecology and vagility. We investigated whether broad‐scale phylogeographic patterns common to a number of small‐bodied vertebrate and invertebrate species in eastern Australian forests were reflected in the population genetic structure of an Australo‐Papuan forest marsupial, the red‐legged pademelon (Macropodidae: Thylogale stigmatica). Strong genetic structuring of mtDNA haplotypes indicated the persistence of T. stigmatica populations across eastern Australia and southern New Guinea in Pleistocene refugial areas consistent with those inferred from studies of smaller, poorly dispersing species. However, there was limited divergence of haplotypes across two known historical barriers in the northeastern Wet Tropics (Black Mountain Barrier) and coastal mideastern Queensland (Burdekin Gap) regions. Lack of divergence across these barriers may reflect post‐glacial recolonization of forests from a large, central refugium in the Wet Tropics. Additionally, genetic structure is not consistent with the present delimitation of subspecies T. s. wilcoxi and T. s. stigmatica across the Burdekin Gap. Instead, the genetic division occurs further to the south in mideastern Queensland. Thus, while larger‐bodied marsupials such as T. stigmatica did persist in Pleistocene refugia common to a number of other forest‐restricted species, species‐specific local extinction and recolonization events have resulted in cryptic patterns of genetic variation. Our study demonstrates the importance of understanding individualistic responses to historical climate change in order to adequately conserve genetic diversity and the evolutionary potential of species.     

Comparative multi-locus phylogeography confirms multiple vicariance events in co-distributed rainforest frogs

Though Pleistocene refugia are frequently cited as drivers of species diversification, comparisons of molecular divergence among sister species typically indicate a continuum of divergence times from the Late Miocene, rather than a clear pulse of speciation events at the Last Glacial Maximum. Community-scale inference methods that explicitly test for multiple vicariance events, and account for differences in ancestral effective population size and gene flow, are well suited for detecting heterogeneity of species' responses to past climate fluctuations. We apply this approach to multi-locus sequence data from five co-distributed frog species endemic to the Wet Tropics rainforests of northeast Australia. Our results demonstrate at least two episodes of vicariance owing to climate-driven forest contractions: one in the Early Pleistocene and the other considerably older. Understanding how repeated cycles of rainforest contraction and expansion differentially affected lineage divergence among co-distributed species provides a framework for identifying evolutionary processes that underlie population divergence and speciation.     

Persistence in peripheral refugia promotes phenotypic divergence and speciation in a rainforest frog

It is well established from the fossil record and phylogeographic analyses that late Quaternary climate fluctuations led to substantial changes in species' distribution, but whether and how these fluctuations resulted in phenotypic divergence and speciation is less clear. This question can be addressed through detailed analysis of traits relevant to ecology and mating within and among intraspecific lineages that persisted in separate refugia. In a biogeographic system (the Australian Wet Tropics [AWT]) with a well-established history of refugial isolation during Pleistocene glacial periods, we tested whether climate-mediated changes in distribution drove genetic and phenotypic divergence in the rainforest frog Cophixalus ornatus. We combined paleomodeling and multilocus genetics to demonstrate long-term persistence within, and isolation among, one central and two peripheral refugia. In contrast to other AWT vertebrates, the three major lineages differ in ecologically relevant morphology and in mating call, reflecting divergent selection and/or genetic drift in the peripheral isolates. Divergence in mating call and contact zone analyses suggest that the lineages now represent distinct species. The results show that climate shifts can promote genetic and phenotypic divergence and, potentially, speciation and direct attention toward incorporating adaptive traits into phylogeographic studies to better resolve the mechanisms of speciation.     

Assessing regulating and provisioning ecosystem services in a contrasting tropical forest landscape

Ecosystem services are the bridge between nature and society, and are essential elements of community well-being. The Wet Tropics Australia, is environmentally and biologically diverse, and supplies numerous ecosystem services. It contributes to the community well-being of this region, Australian national economy and global climate change mitigation efforts. However, the ecosystem services in the region have rarely been assessed undermining strategic landscape planning to sustain their future flow. In this study, we attempted to: (i) assess the quantity of five regulating ecosystem services – global climate regulation, air quality regulation, erosion regulation, nutrient regulation, and cyclone protection, and three provisioning ecosystem services – habitat provision, energy provision and timber provision across rainforests, sclerophyll forests and rehabilitated plantation forests; (ii) evaluate the variation of supply of those regulating and provisioning ecosystem services across environmental gradients, such as rainfall, temperature, and elevation; (iii) show the relationships among those ecosystem services; and (iv) identify the hotspots of single and multiple ecosystem services supply across the landscape. The results showed that rainforests possess a very high capacity to supply single and multiple ecosystem services, and the hotspots for most of the regulating and provisioning ecosystem services are found in upland rainforest followed by lowland rainforest, and upland sclerophyll forest. Elevation, rainfall and temperature gradients along with forest structure are the main determinant factors for the quantity of ecosystem services supplied across the three forest types. The correlation among ecosystem services may be positive or negative depending on the ecosystem service category and vegetation type. The rehabilitated plantation forests may provide some ecosystem services comparable to the rainforest. The results demonstrated disturbance regimes (such as tropical cyclones) may have influenced the usual spatial trend of ecosystem service values. This study will assist decision makers in incorporating ecosystem services into their natural resource management planning, and for practitioners to identify the areas with higher values of specific and multiple ecosystem services.     

Climate refugia and migration requirements in complex landscapes

All of today's species have proven their ability to cope with climate change during the glacial‐interglacial cycles of the Quaternary, but future migration requirements may be different regarding speed, direction, geographic barriers, and availability of nearby climate refugia. Here, we contribute a landscape‐level climatic analysis of postglacial vs. projected future migration requirements for 24 common western North American tree species. Using a recently developed velocity of climate change algorithm, we quantify required migration velocities for all populations of species to track climate habitat, based on projections from general circulation models for the 2080s and the last glacial maximum, 21 000 yr ago. Specifically, we ask if nearby climate refugia exist for at least some populations within species ranges and whether the current landscape position of species imply qualitatively different migration requirements in the future compared to those during glacial‐interglacial cycles. Results showed that velocities to reach the nearest climate refugia in the future still exceed the fastest reconstructed post‐glacial migration requirements, but not by orders of magnitude. Regarding landscape positions, we find a low correlation among past and future migration requirements (r = 0.38), suggesting that qualitatively different migration patterns may emerge in the future for some species. Species identified as occupying landscape positions requiring disproportionally faster migration requirements in the future include whitebark pine, pinyon pine, and coast redwood. We discuss uncertainties of our analytical approach as well as implications for human‐assisted migration and conservation action to address climate change.     

Deeply divergent mitochondrial lineages reveal patterns of local endemism in chironomids of the Australian Wet Tropics

The Wet Tropics bioregion of north‐eastern Australia has been subject to extensive fluctuations in climate throughout the late Pliocene and Pleistocene. Cycles of rainforest contraction and expansion of dry sclerophyll forest associated with such climatic fluctuations are postulated to have played a major role in driving geographical endemism in terrestrial rainforest taxa. Consequences for the distributions of aquatic organisms, however, are poorly understood. The Australian non‐biting midge species Echinocladius martini Cranston (Diptera: Chironomidae), although restricted to cool, well‐forested freshwater streams, has been considered to be able to disperse among populations located in isolated rainforest pockets during periods of sclerophyllous forest expansion, potentially limiting the effect of climatic fluctuations on patterns of endemism. In this study, mitochondrial COI and 16S data were analysed for E. martini collected from eight sites spanning the Wet Tropics bioregion to assess the scale and extent of phylogeographic structure. Analyses of genetic structure showed several highly divergent cryptic lineages with restricted geographical distributions. Within one of the identified lineages, strong genetic structure implied that dispersal among proximate (<1 km apart) streams was extremely restricted. The results suggest that vicariant processes, most likely due to the systemic drying of the Australian continent during the Plio‐Pleistocene, might have fragmented historical E. martini populations and, hence, promoted divergence in allopatry.     

New approaches to understanding late Quaternary climate fluctuations and refugial dynamics in Australian wet tropical rain forests

Aim We created spatially explicit models of palaeovegetation stability for the rain forests of the Australia Wet Tropics. We accounted for the climatic fluctuations of the late Quaternary, improving upon previous palaeovegetation modelling for the region in terms of data, approach and coverage of predictions. Location Australian Wet Tropics. Methods We generated climate‐based distribution models for broad rain forest vegetation types using contemporary and reconstructed ‘pre‐clearing’ vegetation data. Models were projected onto previously published palaeoclimate scenarios dating to c. 18 kyr bp . Vegetation stability was estimated as the average likelihood that a location was suitable for rain forest through all climate scenarios. Uncertainty associated with model projections onto novel environmental conditions was also tracked. Results Upland rain forest was found to be the most stable of the wet forest vegetation types examined. We provide evidence that the lowland rain forests were largely extirpated from the region during the last glacial maximum, with only small, marginally suitable fragments persisting in two areas. Models generated using contemporary vegetation data underestimated the area of environmental space suitable for rain forest in historical time periods. Model uncertainty resulting from projection onto novel environmental conditions was low, but generally increased with the number of years before present being modelled. Main conclusions Climate fluctuations of the late Quaternary probably resulted in dramatic change in the extent of rain forest in the region. Pockets of high‐stability upland rain forest were identified, but extreme bottlenecks of area were predicted for lowland rain forest. These factors are expected to have had a dramatic impact on the historical dynamics of population connectivity and patterns of extinction and recolonization of dependent fauna. Finally, we found that models trained on contemporary vegetation data can be problematic for reconstructing vegetation patterns under novel environmental conditions. Climatic tolerances and the historical extent of vegetation may be underestimated when artificial vegetation boundaries imposed by land clearing are not taken into account.     

Rainforest refugia and Australia's Wet Tropics

Comparison of mitochondrial DNA variation among populations of three endemic lizard species in Australia''s Wet Tropics rainforest reveals clear evidence of population-level response to Pleistocene rainforest contraction and subsequent expansion. This pattern is repeated in two separate rainforest regions (natural replicates), between which populations have been separated for several million years. Despite evidence for isolation in rainforest refugia, historically reduced effective population size, and recent range expansion, little or no detectable phenotypic evolution has occurred among populations, even those isolated for several million years. These observations suggest that long-term isolation per se, even when combined with major reductions in population size and opportunities for drift and founder effects, is unlikely to be the primary process driving phenotypic divergence and speciation of rainforest vertebrates.     

Multilocus phylogeography of the European ground squirrel: cryptic interglacial refugia of continental climate in Europe

The theory of classical and cryptic Pleistocene refugia is based mainly on historical changes in temperature, and the refugia are usually defined within a latitudinal gradient. However, the gradient of oceanic–continental climate (i.e. longitudinal) was also significantly variable during glacial cycles with important biotic consequences. Range‐wide phylogeography of the European ground squirrel (EGS) was used to interpret the evolutionary and palaeogeographical history of the species in Europe and to shed light on its glacial–interglacial dynamic. The EGS is a steppe‐inhabiting species and the westernmost member of the genus in the Palaearctic region. We have analysed 915 specimens throughout the present natural range by employing mitochondrial DNA sequences (cytochrome b gene) and 12 nuclear microsatellite markers. The reconstructed phylogeography divides the species into two main geographical groups, with deep substructuring within both groups. Bulgaria is the centre of the ancestral area, and it also has the highest genetic diversity within the species. The northernmost group of the EGS survived in the southern part of Pannonia throughout several glacial–interglacial cycles. Animals from this population probably repeatedly colonized areas further to the north and west during the glacial periods, while in the interglacial periods, the EGS distribution contracted back to this Pannonian refugium. The EGS thus represents a species with a glacial expansion/interglacial contraction palaeogeographical dynamics, and the Pannonian and southeastern Balkanian steppes are supported as cryptic refugia of continental climate during Pleistocene interglacials.     

Does biogeographical history matter? Diversity and distribution of lotic midges (Diptera: Chironomidae) in the Australian Wet Tropics

Abstract We examined broad scale patterns of diversity and distribution of lotic Chironomidae (Diptera) within the Wet Tropics bioregion of northern Queensland, Australia. Field surveys across broad latitudinal and altitudinal gradients within the Wet Tropics revealed a fauna of 87 species‐level taxa in 49 genera comprising three main elements: a small genuinely tropical fraction, and larger cosmopolitan and Gondwanan components. The latter group originated when Australia, as part of the ancient Gondwana supercontinent, was situated over Antarctic latitudes with a cooler, wetter climate than today. In the Wet Tropics, cool Gondwanan taxa occurred predominantly in upland and shaded lowland sites, but no species appeared narrowly temperature restricted, and there was no faunal zonation with altitude. Most chironomid species occurred at all latitudes within the Wet Tropics, with no evidence for an enduring effect of the historical rainforest contractions on current‐day distribution patterns. These findings contrast with those for aquatic faunas elsewhere in the world and for the terrestrial Wet Tropics fauna. We relate this to the generally broad environmental tolerances of Australian chironomids, and comment on why the latitudinal diversity gradient does not apply to the Australian chironomid fauna.     

Glacial refugia and the phylogeography of Steller's sea lion (Eumatopias jubatus) in the North Pacific

Mitochondrial DNA sequence data were used to examine the phylogeographic history of Steller's sea lions (Eumetopias jubatus) in relation to the presence of Plio-Pleistocene insular refugia. Cytochrome b and control region sequences from 336 Steller's sea lions reveal phylogenetic lineages associated with continental refugia south of the ice sheets in North America and Eurasia. Phylogenetic analysis suggests the genetic structure of E. jubatus is the result of Pleistocene glacial geology, which caused the elimination and subsequent reappearance of suitable rookery habitat during glacial and interglacial periods. The cyclic nature of geological change produced a series of independent population expansions, contractions and isolations that had analogous results on Steller's sea lions and other marine and terrestrial species. Our data show evidence of four glacial refugia in which populations of Steller's sea lions diverged. These events occurred from approximately 60,000 to 180,000 years BP and thus preceded the last glacial maximum.     

Related changes in biodiversity,insolation and climate in the Atlantic rainforest since the last interglacial

The long-term Colônia record is located in the Atlantic rainforest domain in Brazil (23°52′S 46°42′20″W 900 m a.s.l.). The 780 cm long core CO3 provides a coverage of a complete interglacial/glacial cycle for the first time in a neotropical rainforest. Information on the behavior of tropical climates compared to global changes in temperatures indicates specific climate responses in terms of precipitation at these latitudes. Winter extratropical circulation was very active during the last interglacial and most of the glacial. Floristic composition of the rainforest changed several times in each phase of expansion, twice during the interglacial, and three times during glacial episodes. Araucaria was well developed in the area of São Paulo until the beginning of the first dry phase of the glacial at ca. 50,000 yr B.P. Changes in insolation controlled the expansion of the rainforest and the tropical hydrological cycle as evidenced by a strong precession signal. However precession had no impact on regional climatic features. The two interglacials (MIS 5e and Holocene) showed completely different patterns attesting to the continuous evolution of the forest. The biodiversity index (Shannon–Wiener Index) remained high during both the interglacial and glacial attesting to the permanence of small patches of rainforest refugia during drier phases. The lowest Shannon-Wiener Indexes were recorded between 23,000 and 12,000 yr B.P. and 40,000 and 30,000 yr B.P. and characterize two marked phases of stress for the rainforest.     

Sensitivity of tropical forests to climate change in the humid tropics of north Queensland

An analysis using an artificial neural network model suggests that the tropical forests of north Queensland are highly sensitive to climate change within the range that is likely to occur in the next 50–100 years. The distribution and extent of environments suitable for 15 structural forest types were estimated, using the model, in 10 climate scenarios that include warming up to 1°C and altered precipitation from –10% to +20%. Large changes in the distribution of forest environments are predicted with even minor climate change. Increased precipitation favours some rainforest types, whereas decreased rainfall increases the area suitable for forests dominated by sclerophyllous genera such as Eucalyptus and Allocasuarina. Rainforest environments respond differentially to increased temperature. The area of lowland mesophyll vine forest environments increases with warming, whereas upland complex notophyll vine forest environments respond either positively or negatively to temperature, depending on precipitation. Highland rainforest environments (simple notophyll and simple microphyll vine fern forests and thickets), the habitat for many of the region’s endemic vertebrates, decrease by 50% with only a 1°C warming. Estimates of the stress to present forests resulting from spatial shifts of forest environments (assuming no change in the present forest distributions) indicate that several forest types would be highly stressed by a 1°C warming and most are sensitive to any change in rainfall. Most forests will experience climates in the near future that are more appropriate to some other structural forest type. Thus, the propensity for ecological change in the region is high and, in the long term, significant shifts in the extent and spatial distribution of forests are likely. A detailed spatial analysis of the sensitivity to climate change indicates that the strongest effects of climate change will be experienced at boundaries between forest classes and in ecotonal communities between rainforest and open woodland.     

Phylogeography of Eastern Grey Kangaroos,Macropus giganteus,Suggests a Mesic Refugium in Eastern Australia

Phylogeographic studies around the world have identified refugia where fauna were able to persist during unsuitable climatic periods, particularly during times of glaciation. In Australia the effects of Pleistocene climate oscillations on rainforest taxa have been well studied but less is known about the effects on mesic-habitat fauna, such as the eastern grey kangaroo (Macropus giganteus). The eastern grey kangaroo is a large mammal that is common and widespread throughout eastern Australia, preferring dry mesic habitat, rather than rainforest. As pollen evidence suggests that the central-eastern part of Australia (southeast Queensland and northern New South Wales) experienced cycles of expansion in mesic habitat with contraction in rainforests, and vice versa during glacial and interglacial periods, respectively, we hypothesise that the distribution of the eastern grey kangaroo was affected by these climate oscillations and may have contracted to mesic habitat refugia. From 375 mitochondrial DNA control region sequences from across the distribution of eastern grey kangaroos we obtained 108 unique haplotypes. Phylogenetic analysis identified two clades in Queensland, one of which is newly identified and restricted to a small coastal region in southern Queensland north of Brisbane, known as the Sunshine Coast. The relatively limited geographic range of this genetically isolated clade suggests the possibility of a mesic habitat refugium forming during rainforest expansion during wetter climate cycles. Other potential, although less likely, reasons for the genetic isolation of the highly distinct clade include geographic barriers, separate northward expansions, and strong local adaptation.     

Interglacial genetic diversification of Moussonia deppeana (Gesneriaceae), a hummingbird‐pollinated,cloud forest shrub in northern Mesoamerica

Recent empirical work on cloud forest‐adapted species supports the role of both old divergences across major geographical areas and more recent divergences attributed to Pleistocene climate changes. The shrub Moussonia deppeana is distributed in northern Mesoamerica, with geographically disjunct populations. Based on sampling throughout the species range and employing plastid and nuclear markers, we (i) test whether the fragmented distribution is correlated with main evolutionary lineages, (ii) reconstruct its phylogeographical history to infer the history of cloud forest in northern Mesoamerica and (iii) evaluate a set of refugia/vicariance scenarios for the region and demographic patterns of the populations whose ranges expanded and tracked cloud forest conditions during the Last Glacial Maximum. We found a deep evolutionary split in M. deppeana about 6–3 Ma, which could be consistent with a Pliocene divergence. Comparison of variation in plastid and nuclear markers revealed several lineages mostly congruent with their isolated geographical distribution and restricted gene flow among groups. Results of species distribution modelling and coalescent simulations fit a model of multiple refugia diverging during interglacial cycles. The demographic history of M. deppeana is not consistent with an expanding–contracting cloud forest archipelago model during the Last Glacial Maximum. Instead, our data suggest that populations persisted across the geographical range throughout the glacial cycles, and experienced isolation and divergence during interglacial periods.     

Chloroplast DNA variation in the shrub Justicia areysiana (Acanthaceae) endemic to the monsoon affected coastal mountains of the southern Arabian Peninsula

The monsoon affected mountains of the southern Arabian Peninsula harbour in climatically favoured refugia vegetation elements of palaeo-African origin. To understand better the temporal and spatial differentiation of these refugia, chloroplast variation in Justicia areysiana Deflers (Acanthaceae), a shrub species endemic to the Yemeni and Omani mountains close to the Arabian Sea, was studied using PCR-RFLP and chloroplast microsatellite diversity. Eleven haplotypes were characterized and show a distinct geographical distribution pattern with a deep split between populations from south Yemeni fog oases and those from Hawf Mountains/Dhofar region in east Yemen and south Oman. Very limited haplotype diversity within populations (h_S = 0.15) and a high level of population differentiation (G_ST = 0.81) demonstrate the strong genetic isolation of populations from each other. Past oscillations between humid and arid periods connected with glacial and interglacial episodes in the Pleistocene and Holocene are considered responsible for the observed patterns of genetic variation.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 437–444.