Climatic Relict Research Articles

Why cave planthoppers study matters: are Cixiidae a subtroglophile lineage? (Hemiptera, Fulgoromorpha)

Planthoppers are an interesting and contrasting model among insects for studying the subterranean environments. Their morphological and ethological adaptations to the underground conditions (complete darkness, lower temperatures, high hygrometry, stability of environmental constants, rarefied food sources, etc.), and their worldwide distribution in both temperate and tropical areas make them an interesting model among invertebrates. In this review, we highlight why cave planthoppers study matters, with particular emphasis on the Cixiidae. The two hypotheses proposed, the ‘climatic relict hypothesis’ and the ‘adaptive shift’, are not sufficient enough to clearly understand and explain the drivers to cavernicoly. Phylogenetic analyses approaches might help to better document and increase our knowledge on such peculiar environments. The singularity of the distribution pattern of the adaptation to cavernicoly in planthoppers raises also interesting questions to investigate and suggest contrasting scenarios to explore further, particularly should the Cixiidae be defined as a subtroglophile lineage?

Demographic history and conservation aspects of two relict shrubs (Daphnimorpha spp., Thymelaeaceae) showing disjunct and restricted distribution in the southern part of Japan

Climate relicts are of particular importance in evolutionary biology because of the strategies they may adopt for long-term survival despite climatic oscillations. However, because their current distribution is usually restricted and fragmented, many climatic relicts are at risk of extinction. Daphnimorpha (Thymelaeaceae) is a genus endemic to Japan that comprises two species (D. capitellata and D. kudoi) with a disjunct distribution in southern Japan. These two shrub species are endemic to a single mountain range. In this study, we conducted population genetic analyses using genome-wide single nucleotide polymorphisms obtained from multiplexed inter-simple sequence repeats genotyping by sequencing to reveal the phylogeographic history and obtain conservation implications for the two species. The results showed that these two species may have been isolated since the Tertiary period, supporting their status as climate relicts. In addition, D. kudoi showed clear genetic differentiation between the two mountains where it occurred (Mt. Nagata and Mt. Kuromi), with a decline in the effective population sizes inferred during the last glacial period. In contrast, D. capitellata showed no clear intraspecific genetic structure, and its effective population size was relatively stable. These differences could result in contrasting light tolerance between species. For conservation, we recommend managing these species as three evolutionarily significant units (ESUs): D. capitellata, D. kudoi population on Mt. Nagata, and D. kudoi population on Mt. Kuromi. Considering the limited gene flow among subpopulations and small population census, all ESUs require conservation attention to maintain or increase their effective population sizes.

Environmental heterogeneity increases the conservation value of small natural features in karst landscapes

Local biodiversity hotspots are often located within regions where extreme and variable environmental – e.g., climatic and soil – conditions occur. These areas are conservation priorities. Although environmental heterogeneity is recognised as an important determinant of biodiversity, studies focusing on the effects of multiple environmental heterogeneity components in the same ecosystem are scarce. Here we investigate how topography and related microclimatic variables and soil properties may influence the biodiversity and conservation value of karst landscapes. Karst landscapes of the world contain millions of dolines (i.e. bowl- or funnel-shaped depressions) that may function as ‘small natural features’ with a disproportionately large role in maintaining biodiversity relative to their size. We assessed the diversity of microclimates, soils and vegetation and their relationships in six microhabitats (south-facing slopes, east-facing slopes, west-facing slopes, north-facing slopes and bottoms of dolines, and the adjacent plateau) for nine large dolines in a grassland ecosystem. Although there were remarkable differences among the conservation value of these microhabitats (e.g., representation of different species groups, presence of ‘climate relicts’), each microhabitat had an important role in maintaining species that are rare or absent in other microhabitats in the landscape. We found that the studied dolines exhibited highly variable environmental conditions and promoted a high diversity of vegetation types with unique species composition, contributing to the topographic, climatic, soil, vegetation and land cover heterogeneity of karst landscapes. Therefore, our findings highlight that dolines may function as local biodiversity hotspots and have a crucial conservation importance. As dolines are widespread topographic features in many karst landscapes throughout the world, our results could be directly applied to other regions as well. An integrated approach is urgently needed to provide guidelines for landscape management, promoting the retention of the microhabitat diversity of small natural features for species vulnerable to climate change and/or various disturbances.

Climate Relicts: Asian Scorpion Family Pseudochactidae Survived Miocene Aridification in Caves of the Annamite Mountains

Abstract Southeast Asia is a hotspot of karst systems in the tropics and many relictual taxa have been documented in caves across the region. The ancient, relictual scorpion family Pseudochactidae Gromov 1998 has a disjunct distribution and includes two hypogean subfamilies from caves in the Khammouan-Phong Nha-Kẻ Bàng Karst in the northern Annamite (Trường Sơn) Mountains of Laos and Vietnam, and one epigean subfamily from Central Asia. A recent revision identified six species in the family; however, how these taxa dispersed and diversified into Southeast Asian cave systems has not been tested. In the present contribution, the phylogeny of Pseudochactidae is reconstructed using three mitochondrial and three nuclear markers and 140 morphological characters, divergence time and ancestral range estimation analyses are conducted, and the evolution of troglomorphic characters is investigated. Results confirm a previous hypothesis that Pseudochactidae originated in Eurasia, most likely near the Tajik block in the Carboniferous, supporting the ‘Out of Eurasia’ hypothesis and contradicting the ‘Eurogondwana’ and ‘Out of India’ hypotheses for the origin of Southeast Asian scorpions. Pseudochactidae dispersed across Southeast Asia after the collision of the Cimmerian continent and Indochina with Eurasia in the Late Jurassic. Colonization of Southeast Asian caves began in the Late Cretaceous and was completed by the Miocene. The onset of aridification in Southeast Asia during the Late Miocene resulted in the extinction of epigean Pseudochactidae, whereas hypogean members of the family likely survived within caves in the limestone massifs of the Annamite Mountains, supporting the ‘Climate Relict’ hypothesis.

The pseudoscorpion genus Centrochthonius (Pseudoscorpiones: Pseudotyrannochthoniidae) from central Asia and description of a new species from Nepal

The pseudotyrannochthoniid genus Centrochthonius Beier, 1931 is one of the rarest and most poorly understood pseudoscorpion genera in the world. Only a handful of specimens are presently known, all from high-altitude habitats in China, Kyrgyzstan and Nepal. The inaccessibility of specimens has resulted in major taxonomic difficulties such as a poor generic diagnosis, but also a lack of understanding of evolutionary patterns in this psychrophilic fauna. Herein we diagnose Centrochthonius for the first time since its original description and include four Holocene species: one from Kyrgyzstan, two from China, and C. anatonus sp. nov. from Nepal. A fifth fossil species from Bitterfeld amber (Oligocene-Miocene) in central Europe highlights significant range retraction and continental extinction in this genus since the Neogene, leading us to suggest a climatic relict hypothesis for this fauna. Biogeographically, the genus provides further evidence for significant range shifts and extinction events in the Holarctic invertebrate biota during the Cenozoic. Close relatives of Centrochthonius are found in subterranean habitats throughout eastern Asia and warm temperate forests in the western U.S.A. which highlights the magnitude of range retraction caused by climatic cycling in an ancient fauna since at least the Paleogene. The subgenus Allochthonius (Urochthonius) Morikawa, 1954 from caves in Japan has been largely defined by the presence of troglomorphic features such as eye loss, which are here regarded as insufficient to retain as a separate clade from other species of Allochthonius. Therefore, Allochthonius (Urochthonius) is treated as a junior synonym of Allochthonius (syn. nov.).

Assessing Phenotypic Variability in Some Eastern European Insular Populations of the Climatic Relict Ilex aquifolium L.

Through its natural or cultivated insular population distribution, Ilex aquifolium L. is a paramount species which is exceptionally suitable for studying phenotypic variability and plasticity through the assessment of morphological, physiological, biochemical and genomic features with respect to acclimation and/or adaptation efficiency. The current study is focused on four insular populations of Ilex aquifolium from Eastern Europe (i.e., in Romania, Hungary, Serbia and Bulgaria), and presents an initial evaluation of phenotypic variability in order to conclude our research on phylogenetic relationships and phytochemical profiles, including several descriptive and quantitative morphological traits. Taken together, the data from different methods in this paper indicate that the Bulgarian and Romanian populations can be distinguished from each other and from Serbian and Hungarian populations, while the latter show a higher level of resemblance with regards to their quantitative morphological traits. It is likely that these morphological traits are determined through some quantitative trait loci implicated in stress responses generated by light, temperature, soil water, soil fertility and salinity conditions that will need to be analysed in terms of their physiological, genomic and metabolomics traits in future studies.

Overcoming shortfalls and impediments in subterranean biology: a challenge for the future

Since the discovery and description of the first specialized cave species, subterranean fauna stimulated the scientific research of several generations of speleobiologists especially after the publication of Racovitza's classification of cave species, which is still used today, amended for non-karstic areas and groundwaters. More than 28,000 obligate subterranean species are known worldwide; however, these figures are likely to be underestimated since species richness is highly correlated with research effort (Stoch and Galassi 2010). Subterranean ecosystems are very rich in strict endemic species and taxonomic efforts are still quite low (i.e., the so-called "taxonomic impediment"), while several environments are very difficult to be explored (i.e., the "Racovitzan impediment: Ficetola et al. 2018). Furthermore, several paradigms were debated for years. Albeit constrasting hypotheses were conceived to explain the colonization of subsurface habitats, their importance is still debated (i.e., climate relicts vs. adaptive shift in colonization and speciation, dispersal vs. vicariance in shaping distributional patterns, and selective vs. neutral hypotheses in explaining regressive evolution). Moreover, the paradigm of a "truncated functional diversity" of subterranean ecosystems (Gibert and Deharveng 2002) lasted for years but was recently challenged by the discovery of chemoautotrophic ecosystems in hypogenic and anchialine caves, and the recognition that caves are not isolated environments, but they are highly interconnected with surface ecosystems. The increased importance of their conservation (like in the case of GDEs, Groundwater Dependent Ecosystems) was recently recognized, together with their provision of important ecosystem services (Boulton 2020). A deeper knowledge is required to assess biodiversity hotspots as well as to plan efficient monitoring surveys (Mammola et al. 2020). In the last decades, a growing amount of molecular data has been obtained for subterranean species, allowing some of the classical debates on colonization, evolution, and dispersal to be revisited (Bauzà-Ribot et al. 2012); moreover, novel promising techniques like metabarcoding and environmental DNA were applied in field surveys and monitoring efforts. Unfortunately, after more than one century of research in subterranean biology, large gaps remain in our knowledge of phylogeny, richness, and distribution of subterranean fauna (formalized in the so-called Darwinian, Linnean and Wallacean shortfalls), preventing the definition of large-scale sound management and protection plans. It is proposed that data from recent biomolecular techniques coupled with remotely sensed data may enhance biodiversity mapping and conservation and are promising approaches to fill our knowledge gaps. Perhaps this is the greatest challenge that tomorrow's subterranean biologists will face.

Riding the elevator to extinction: Disjunct arctic-alpine plants of open habitats decline as their more competitive neighbours expand

Major displacement of arctic-alpine species towards higher elevations and latitudes is anticipated under climate warming. Disjunct plant populations persisting on mountains at the limits of their species' distributions may have a reduced capacity for migration, and therefore offer a particularly sensitive indication of climate change effects. The flora of Scotland's mountains is of international significance because it contains populations of climate relicts which are isolated geographically and located at the rear edge of their global range. We used a unique long-term monitoring dataset recording vegetation change at a mountain outpost site in the Scottish Highlands to identify divergent population trends in ten rare plant species over the last 30 years. Three arctic-alpine specialists (Sagina nivalis, Sabulina rubella and Saxifraga cernua) have suffered severe declines of over 50 % of their population size since the mid-1990s, and have been extirpated at their lowest altitude locations. These species are undergoing elevational range contractions and Sagina nivalis is now considered Endangered in Britain. Their open, gravelly snowbed habitats have been affected by vegetation encroachment, landslip and rockfalls. Population changes across all species studied were also significantly related to altitude. Species with stable or increasing population sizes occur at lower altitudes, are taller and have less reliance on sparsely vegetated habitats. These results can be contextualised within broad trends of thermophilization, biotic homogenization, mountain greening and snow cover declines. Our work demonstrates that disjunct low-latitude arctic-alpine plant populations already situated at maximum local elevational gradients could face “mountaintop extinction”, with implications for the conservation of regional biodiversity.

Are Cenozoic relict species also climatic relicts? Insights from the macroecological evolution of the giant sedges of Carex sect. Rhynchocystis

Are Cenozoic relict species also climatic relicts? Insights from the macroecological evolution of the giant sedges of Carex sect. Rhynchocystis

Are Cenozoic relict species also climatic relicts? Insights from the macroecological evolution of the giant sedges of Carex sect. Rhynchocystis (Cyperaceae).

Most of the Paleotropical flora widely distributed in the Western Palearctic became extinct during the Mio-Pliocene as a result of global geoclimatic changes. A few elements from this Cenozoic flora are believed to remain as relicts in Macaronesia, forming part of the laurel forests. Although the origins of the present species assembly are known to be heterogeneous, it is unclear whether some species should be considered climatic relicts with conserved niches. An ideal group for studying such relict characteristics is a Miocene lineage of Carex sect. Rhynchocystis (Cyperaceae), which comprises four species distributed in mainland Palearctic and Macaronesia. We reconstructed the current and past environmental spaces for extant mainland and Macaronesian species, as well as for Pliocene fossils. We also studied the bioclimatic niche evolution. Species distribution modeling and ensemble small modeling were performed to assess the potential distribution over time. Climatic niche analyses and distribution modeling revealed that the ecological requirements of Macaronesian species did not overlap with those of either mainland species or with the Pliocene fossils. Conversely, the niches of mainland species displayed significant similarity and equivalence. Macaronesian species are not climatic relicts from the Paleotropical flora, but instead seem to have changed the ecological niche of their ancestors. By contrast, despite their ancient divergence (Late Miocene), mainland C. pendula and C. agastachys show conserved niches, with competitive exclusion likely shaping their mostly allopatric ranges.

Climate relict vulnerable to extinction from multiple climate‐driven threats

AbstractAimOver the gradually warming Holocene, many species’ range limits shifted poleward. However, some populations persisted in climate refugia, such as mountain tops. These climate relict populations are critical components of regional biodiversity, but their isolation renders them vulnerable to other threats, including changes in environmental conditions indirectly related to a warming global climate. We aimed to quantify the role of these indirect climate effects on Florida saltmarsh vole (Microtus pennsylvannicus dukecampbelli; hereafter: “vole”), a poorly understood, endangered climate relict.LocationThe Gulf of Mexico between Sopchoppy and Pine Island, Florida, USA.MethodsWe surveyed for voles broadly across their potential range using camera traps and modelled the relationships between vole occurrence and two climate‐driven threats: hurricane storm surge and shifting vegetation communities. We quantified these threats using both field‐collected and remotely sensed data at fine (3‐m) and coarse (150‐m) spatial scales.ResultsThough seemingly suitable habitat exists outside their previously known range, voles appeared restricted to the outer marshes between the Suwannee and Withlacoochee Rivers. Within this range, the sites we surveyed had shorter grass heights, greater Distichils spp. cover, greater potential habitat within 150 m, and were less vulnerable to inundation when compared to sites outside of their range.Main conclusionsThe complex and varied ways in which climate change alters the physical environment can expose small‐ranging species to multiple threats. Even climate relicts, which have endured historical changes in the global climate, may fail to cope with the rapid pace of anthropogenic climate change.

Mesofauna at the Soil-Scree Interface in a Deep Karst Environment

The community patterns of Collembola (Hexapoda) were studied at two sites along a microclimatically inversed scree slope in a deep karst valley in the Western Carpathians, Slovakia, in warm and cold periods of the year, respectively. Significantly lower average temperatures in the scree profile were noted at the gorge bottom in both periods, meaning that the site in the lower part of the scree, near the bank of creek, was considerably colder and wetter compared to the warmer and drier site at upper part of the scree slope. Relatively high diversity of Collembola was observed at two fieldwork scree sites, where cold-adapted species, considered climatic relicts, showed considerable abundance. The gorge bottom, with a cold and wet microclimate and high carbon content even in the deeper MSS horizons, provided suitable environmental conditions for numerous psychrophilic and subterranean species. Ecological groups such as trogloxenes and subtroglophiles showed decreasing trends of abundance with depth, in contrast to eutroglophiles and a troglobiont showing an opposite distributional pattern at scree sites in both periods. Our study documented that in terms of soil and subterranean mesofauna, colluvial screes of deep karst gorges represent (1) a transition zone between the surface and the deep subterranean environment, and (2) important climate change refugia.

Inferring historical survivals of climate relicts: the effects of climate changes, geography, and population-specific factors on herbaceous hydrangeas.

Climate relicts hold considerable importance because they have resulted from numerous historical changes. However, there are major interspecific variations among the ways by which they survived climate changes. Therefore, investigating the factors and timing that affected population demographics can expand our understanding of how climate relicts responded to historical environmental changes. Here, we examined herbaceous hydrangeas of genus Deinanthe in East Asia, which show limited distributions and a remarkable disjunction between Japan and central China. Chloroplast genome and restriction site-associated DNA sequencing revealed that speciation event occurred in the late Miocene (ca. 7-9 Mya) in response to global climate change. Two lineages apparently remained not branched until the middle Quaternary, and afterwards started to diverge to regional population groups. The narrow endemic species in central China showed lower genetic diversity (He = 0.082), as its population size rapidly decreased during the Holocene due to isolation in montane refugia. Insular populations in the three Japanese islands (He = 0.137-0.160) showed a genetic structure that was inconsistent with sea barriers, indicating that it was shaped in the glacial period when its range retreated to coastal refugia on the exposed sea floor. Demographic modelling by stairway-plot analysis reconstructed variable responses of Japanese populations: some experienced glacial bottlenecks in refugial isolation, while post-glacial range expansion seemingly exerted founder effects on other populations. Overall, this study demonstrated the involvement of not just one, but multiple factors, such as the interplay between climate changes, geography, and other population-specific factors, that determine the demographics of climate relicts.

Fagus sylvatica L. Peripheral Populations in the Mediterranean Iberian Peninsula: Climatic or Anthropic Relicts?

European beech is a temperate species with peripheral populations in the Mediterranean mountains. These Mediterranean beech forests have often been interpreted as climatic relicts. However, the use of this term does not always seem appropriate because their recent post-glacial expansion in the Iberian Peninsula makes it difficult to disentangle the effects of climate from those associated with land use. Moreover, the observed recovery of Mediterranean beech forests after landuse abandonment is not what might be expected of a climatic relict. Our objective is to clarify this issue by studying one of these Mediterranean ‘‘relict’’ populations located at the south-western margin of this species (Iberian Central Range), discriminating between subpopulations with dissimilar land-use legacies. Differences between the climatic range of this population and the rest of the European beech forests were explored. Historic and recent shifts in the species distribution area were studied by reviewing paleorecords from the literature and contrasting historical and recent cartography. Field data on population structure and demography were also examined. The climatic analyses do not point to climatic marginality of the peripheral population studied. Furthermore, the results revealed no evidence of reduction in area or confinement over recent decades. Contrary to what is expected for climatic relict species under current climate, beech is expanding in the studied mountain following the abandonment of traditional land uses, particularly since the middle of the twentieth century CE. Our results do not support the concept of a climatic relict but rather, they point to the importance of anthropogenic legacies to explain the distribution area, population dynamics and current conservation status of Mediterranean beech forests.

Ice-age persistence and genetic isolation of the disjunct distribution of larch in Alaska.

Larix laricina (eastern larch, tamarack) is a transcontinental North American conifer with a prominent disjunction in the Yukon isolating the Alaskan distribution from the rest of its range. We investigate whether in situ persistence during the last glacial maximum (LGM) or long‐distance postglacial migration from south of the ice sheets resulted in the modern‐day Alaskan distribution. We analyzed variation in three chloroplast DNA regions of 840 trees from a total of 69 populations (24 new sampling sites situated on both sides of the Yukon range disjunction pooled with 45 populations from a published source) and conducted ensemble species distribution modeling (SDM) throughout Canada and United States to hindcast the potential range of L. laricina during the LGM. We uncovered the genetic signature of a long‐term isolation of larch populations in Alaska, identifying three endemic chlorotypes and low levels of genetic diversity. Range‐wide analysis across North America revealed the presence of a distinct Alaskan lineage. Postglacial gene flow across the Yukon divide was unidirectional, from Alaska toward previously glaciated Canadian regions, and with no evidence of immigration into Alaska. Hindcast SDM indicates one of the broadest areas of past climate suitability for L. laricina existed in central Alaska, suggesting possible in situ persistence of larch in Alaska during the LGM. Our results provide the first unambiguous evidence for the long‐term isolation of L. laricina in Alaska that extends beyond the last glacial period and into the present interglacial period. The lack of gene flow into Alaska along with the overall probability of larch occurrence in Alaska being currently lower than during the LGM suggests that modern‐day Alaskan larch populations are isolated climate relicts of broader glacial distributions, and so are particularly vulnerable to current warming trends.

СУББОРЕАЛЬНЫЕ ЭЛЕМЕНТЫ В ЛЕПИДОПТЕРОФАУНЕ (LEPIDOPTERA) ЕВРОПЕЙСКОГО СЕВЕР О-ВОСТОКА РОССИИ

Based on the material of Macrolepidoptera, high percentage of in the taiga and tundra biota of subboreal geographical elements – one of the main biogeographic features of the European North-East of Russia – is considered. It is shown that over 50 species of Lepidoptera from 11 families have peripheral area covers in various extent taiga zone and the southern parts of Hypoarctic zone, and the area of their ecological optimum situated in the subboreal forest and steppe zones. In consideration of peculiarities of the natural process, the analysis of the landscape-zonal distribution of Lepidoptera species suggests that the penetration of subboreal species was began and gradually took place during the warm periods of Holocene. A few groups of Holocene climatic relicts have been preserved in various areas of the taiga and the foresttundra zones. At the present time the most of subboreal species of Lepidoptera in the European North- East of Russia are new and actively distributing in anthropogenic habitats.

Thermal Constraints Explain the Distribution of the Climate Relict Lizard Colobosauroides carvalhoi (Gymnophthalmidae) in the Semiarid Caatinga

Within the semiarid Caatinga of Brazil, a biome dominated by a xeric arboreal-arbustive vegetation, many lizards are restricted to forest remnants associated with highlands. Although critical for conservation, data to understand the constraints on the distribution of those potential climate relicts are almost nonexistent. Here, we studied aspects of the ecology of the relict forest lizard Colobosauroides carvalhoi (Gymnophthalmidae) in the Caatinga of southern Piaui, northeastern Brazil. We combined data obtained through active sampling with voluntary thermal maximum (VTM) and measurements of environmental temperatures made in different habitats, microhabitats, and seasons to test the prediction that thermal constraints explain the local distribution and abundance of this species. In four field trips, we captured 22 individuals in pitfall traps and 93 in active searches, all in canyon-like valleys covered with semi-deciduous forests. Using plot sampling, we observed that density decreased as distance from rock cliffs increased. Density did not differ among sampling localities but varied among seasons. Field body temperatures were similar to soil temperatures under the leaf litter and lower than air and surface temperatures. Environmental temperatures in forests were lower than the VTM estimated for C. carvalhoi, especially under the leaf litter. Nevertheless, environmental temperatures usually exceeded the VTM at forest borders and in caatingas, in which the species was absent. Our results confirm that C. carvalhoi is spatially constrained to patches of semi-deciduous forests and suggest that its low thermal tolerance likely prevents it from occurring or dispersing through xeric habitats that predominates in Caatinga.

Biogeographic history of subterranean isopods from groundwater calcrete islands in Western Australia

Groundwater calcretes in arid central Western Australia contain a diverse invertebrate groundwater fauna (stygofauna). Surveys have uncovered a diverse oniscidean isopod subterranean fauna above the water table (troglofauna), including species of a recently described genus Paraplatyarthrus. The aim of this study was to investigate the biogeographic history of Paraplatyarthrus and the timing of transitions from surface to subterranean habitats. Phylogenetic relationships among the isopod troglofauna from 11 groundwater calcretes along three palaeodrainage systems were assessed using one mitochondrial gene, cytochrome c oxidase subunit 1 (COI), and two nuclear markers, lysyl‐tRNA synthetase (LysRS) and 18S rRNA (18S) genes. Phylogenetic analyses revealed multiple sister lineage relationships between troglophile and troglobite lineages and evidence for divergent mtDNA lineages within species, providing a range of nodes for dating evolutionary transitions from surface to subterranean habitats. Relaxed molecular clock analyses provided evidence that evolutionary transitions from surface to subterranean environments took place between 13.3 and 1.75 million years ago, coinciding with the onset of aridification of Australia from the late Tertiary. In cases where groundwater calcretes contained multiple species, the taxa were not closely related phylogenetically, suggesting that these calcretes were independently colonised by multiple ancestral species. The study further confirmed the role of late/post‐Miocene aridification as a key driver of the evolution of subterranean invertebrates in the calcrete islands of Western Australia, supporting the climatic relict hypothesis. Troglobites most likely evolved from the troglophile ancestors that were capable of dispersal among, and active colonisation of, calcretes.

Diversification in tropics and subtropics following the mid-Miocene climate change: A case study of the spider genus Nesticella.

Caves may offer suitable refugia for troglophilic invertebrates during periods of unfavourable climatic conditions because of their stable microclimates. As a consequence, allopatric divergence from their epigean counterparts may occur, leading to formation of truly hypogean communities (the Climatic Relict Hypothesis). Unlike the well-studied effects of Pleistocene glaciations, we know little about how ancient climate changes drove the development of cave-dwelling organisms living at both middle and lower latitudes. We investigate the evolutionary history of the troglophilic spider genus Nesticella (Araneae, Nesticidae) in relation to Asian Neogene (23-2.6Ma) climatic changes. Our analyses discern clear differences in the evolution of the two main clades of Nesticella, which occur in temperate/subtropical and tropical latitudes. Eastern Asian Nesticella gradually evolved greater sedentariness and a strict subterranean lifestyle starting from the middle Miocene Epoch (~15-14Ma) in conjunction with the progressive deterioration of the climate and vegetational shifts. Caves appear to have acted as refugia because of their internally uniform temperature and humidity, which allowed these spiders to survive increasing external seasonality and habitat loss. In contrast, a uniform accumulation of lineages, long-lasting times for dispersals and the lack of a comparable habitat shifting characterized the tropical lineage. This difference in pattern likely owes to the mild effects of climate change at low latitudes and the consequent lack of strong climatic drivers in tropical environments. Thus, the mid-Miocene climatic shift appears to be the major evolutionary force shaping the ecological differences between Asian troglophilic invertebrates and the driver of the permanent hypogean communities in middle latitudes.

Identification of Floral Relicts Based on Spatial Distance of Isolation

The identification of climatic relicts is seldom straightforward. These species are threatened owing to current climatic trends, which underlines the importance of carrying out ecological and biogeographic investigations of them. Here we introduce a novel approach to improve the identification of climatic relicts. We are focusing on thermophilic relict plants of the Pannonian biogeographic region from the Holocene Thermal Maximum (HTM). We argue that a minimal mean annual temperature difference (MATD) of the HTM compared to the recent climate allowed a continuous northward expansion for the taxa investigated. We measured latitudinal distances between the recent occurrences of relicts and those of the main distribution found further south. Regarding estimates for MATD (1.0–2.5 °C), we only consider species with a distribution which has a 150–350 km North-South gap, since a latitudinally directed distance can be translated into temperature, showing a poleward cooling trend. Of the 15 selected species, 12 were recorded with values of 1.0–1.7 °C MATD, and three with values of 1.8–2.5 °C, some of which are presumably interglacial species. Woody species are over-represented among them (four species), using the Hungarian flora as a reference. The proposed method allows the prediction of potential climate-related changes in the future distribution of species, constrained by the topographic features of their habitats.