Tree species and microhabitat influence the population structure of the epiphytic lichen Lobaria pulmonaria

Detailed knowledge of the habitat requirements of species is required because habitat greatly affects the persistence of species. We investigated the effects of tree species and microhabitat heterogeneity on the population of the locally threatened lichen Lobaria pulmonaria. We studied four L. pulmonaria populations in Central Spain and collected microhabitat data for individuals growing on beech and oak. The microhabitat affected the life stages of L. pulmonaria; being a phorophyte species the location of the lichen was the most important factor generating different patterns of establishment, abundance, thallus size and reproductive capacity. Although oak forests favoured the establishment and recruitment of new L. pulmonaria individuals, they apparently provided adverse environmental conditions for lichen growth, thus affecting the reproductive capacity since this is size-dependent. By contrast, beech forests offered a more favourable microclimate, because L. pulmonaria individuals reached larger sizes in these forests. In conclusion, our results indicate that habitats hosting large populations, with high rates of establishment and recruitment do not necessarily favour other life-cycle stages.     

Algal and Fungal Diversity in Antarctic Lichens

The composition of lichen ecosystems except mycobiont and photobiont has not been evaluated intensively. In addition, recent studies to identify algal genotypes have raised questions about the specific relationship between mycobiont and photobiont. In the current study, we analyzed algal and fungal community structures in lichen species from King George Island, Antarctica, by pyrosequencing of eukaryotic large subunit (LSU) and algal internal transcribed spacer (ITS) domains of the nuclear rRNA gene. The sequencing results of LSU and ITS regions indicated that each lichen thallus contained diverse algal species. The major algal operational taxonomic unit (OTU) defined at a 99% similarity cutoff of LSU sequences accounted for 78.7–100% of the total algal community in each sample. In several cases, the major OTUs defined by LSU sequences were represented by two closely related OTUs defined by 98% sequence similarity of ITS domain. The results of LSU sequences indicated that lichen‐associated fungi belonged to the Arthoniomycetes, Eurotiomycetes, Lecanoromycetes, Leotiomycetes, and Sordariomycetes of the Ascomycota, and Tremellomycetes and Cystobasidiomycetes of the Basidiomycota. The composition of major photobiont species and lichen‐associated fungal community were mostly related to the mycobiont species. The contribution of growth forms or substrates on composition of photobiont and lichen‐associated fungi was not evident.     

European phylogeography of the epiphytic lichen fungus Lobaria pulmonaria and its green algal symbiont

In lichen symbiosis, fungal and algal partners form close associations, often codispersed by vegetative propagules. Due to the particular interdependence, processes such as colonization, dispersal or genetic drift are expected to result in congruent patterns of genetic structure in the symbionts. To study the population structure of an obligate symbiotic system in Europe, we genotyped the fungal and algal symbionts of the epiphytic lichen Lobaria pulmonaria at eight and seven microsatellite loci, respectively, and analysed about 4300 L. pulmonaria thalli from 142 populations from the species' European distribution range. Based on a centroid approach, which localizes centres of genetic differentiation with a high frequency of geographically restricted alleles, we identified the South Italy–Balkan region as the primary glacial refugial area of the lichen symbiosis. Procrustean rotation analysis and a distance congruence test between the fungal and algal population graphs indicated general concordance between the phylogeographies of the symbionts. The incongruent patterns found in areas of postglacial recolonization may show the presence of an additional refugial area for the fungal symbiont, and the impact that horizontal photobiont transmission and different mutation rates of the symbionts have on their genotypic associations at a continental scale.     

Fungal farmers or algal escorts: lichen adaptation from the algal perspective

Domestication of algae by lichen‐forming fungi describes the symbiotic relationship between the photosynthetic (green alga or cyanobacterium; photobiont) and fungal (mycobiont) partnership in lichen associations ( Goward 1992 ). The algal domestication implies that the mycobiont cultivates the alga as a monoculture within its thallus, analogous to a farmer cultivating a food crop. However, the initial photobiont ‘selection’ by the mycobiont may be predetermined by the habitat rather than by the farmer. When the mycobiont selects a photobiont from the available photobionts within a habitat, the mycobiont may influence photobiont growth and reproduction ( Ahmadjian & Jacobs 1981 ) only after the interaction has been initiated. The theory of ecological guilds ( Rikkinen et al. 2002 ) proposes that habitat limits the variety of photobionts available to the fungal partner. While some studies provide evidence to support the theory of ecological guilds in cyanobacterial lichens ( Rikkinen et al. 2002 ), other studies propose models to explain variation in symbiont combinations in green algal lichens ( Ohmura et al. 2006 ; Piercey‐Normore 2006 ; Yahr et al. 2006 ) hypothesizing the existence of such guilds. In this issue of Molecular Ecology, Peksa & ?kaloud (2011) test the theory of ecological guilds and suggest a relationship between algal habitat requirements and lichen adaptation in green algal lichens of the genus Lepraria. The environmental parameters examined in this study, exposure to rainfall, altitude and substratum type, are integral to lichen biology. Lichens have a poikilohydric nature, relying on the availability of atmospheric moisture for metabolic processes. Having no known active mechanism to preserve metabolic thallus moisture in times of drought, one would expect a strong influence of the environment on symbiont adaptation to specific habitats. Adaptation to changes in substrata and its properties would be expected with the intimate contact between crustose lichens in the genus Lepraria. Altitude has been suggested to influence species distributions in a wide range of taxonomic groups. This is one of the first studies to illustrate an ecological guild, mainly for exposure to rainfall (ombrophiles and ombrophobes), with green algal lichens.     

Diversity and Coexistence of Ectoparasites in Small Rodents in a Tropical Dry Forest

To understand the mechanisms driving species diversity is central to community ecology. Here, we explored if habitat partitioning is associated with a species‐rich ectoparasite community in small rodents from a tropical dry forest in western Mexico. We trapped 199 mice in three 0.5 ha‐plots from eight small rodent species for every two months, from July 2011 to April 2012, and collected their ectoparasites. We identified 17 species of mites, two sucking lice species, two phoretic species, and one commensal species. The most abundant ectoparasite species was Steptolaelaps liomydis, representing 42 percent of all ectoparasites collected; seven ectoparasite species had < 10 individuals. Eighteen ectoparasite species (of 22 species) were collected from the most abundant rodent Liomys pictus. C‐score and the number of checkerboard species pairs were significantly higher against a random expectation. Ectoparasite species in L. pictus mice showed host microhabitat partitioning; Fahrenholzia ehrlichi and Fahrenholzia texana were found only in the anterior dorsal area, Ornithonysus sp. occurred along the dorsal part, Ixodes species were restricted to the ears, and Steptolaelaps liomydis was found throughout the body. We also identified ectoparasite communities with distinct species composition in two rodent species that use contrasting macrohabitats (L. pictus, strictly terrestrial; Peromyscus perfulvus, mostly arboreal). The remaining and low abundant rodent species showed a species‐poor ectoparasite community composition. We conclude that habitat partitioning at both macro and microhabitat scales appeared to characterize the species‐rich ectoparasite community. Conversely, most rodent host species with low abundances showed a species‐poor ectoparasite community.     

Fungal melanins as a sun screen for symbiotic green algae in the lichen<Emphasis Type="Italic"> Lobaria pulmonaria</Emphasis>

The mycobiont of the high-light-susceptible forest lichen Lobaria pulmonaria was shown to deposit brown, melanic compounds in the outer layer of the upper cortex, depending on the long-term level of solar radiation in its natural habitat. Furthermore, pale thalli from a shady habitat produced melanic compounds after transplantation to a sunny habitat. This browning of the cortex appeared to be a physiologically active process, taking place only during periods with frequent hydration. Melanin production was slow. After transplantation, more than 1 year was needed for a shade-adapted thallus to reduce the cortical transmittance (230-1000 nm) to a similar level to that of naturally sun-exposed specimens. Melanic compounds acted as a sun screen, especially reducing UVB and UVA wavelengths, but also visible wavelengths, at the photobiont level. In the near infrared range, there was only a small difference in transmittance between shade- and sun-adapted cortices. A negative correlation was found between the natural light level and the cortical transmittance of wavelengths below 700 nm. However, previous studies have shown that even photobionts of melanic L. pulmonaria thalli are relatively susceptible to high-light exposure. Since melanins also increase the absorbance of solar energy for the whole thallus, it appears that what is gained in terms of UV- and light protection in melanic L. pulmonaria specimens may be offset by increased exposure to excess temperatures for this highly heat-susceptible lichen.     

Fungal specificity and selectivity for algae play a major role in determining lichen partnerships across diverse ecogeographic regions in the lichen‐forming family Parmeliaceae (Ascomycota)

Microbial symbionts are instrumental to the ecological and long‐term evolutionary success of their hosts, and the central role of symbiotic interactions is increasingly recognized across the vast majority of life. Lichens provide an iconic group for investigating patterns in species interactions; however, relationships among lichen symbionts are often masked by uncertain species boundaries or an inability to reliably identify symbionts. The species‐rich lichen‐forming fungal family Parmeliaceae provides a diverse group for assessing patterns of interactions of algal symbionts, and our study addresses patterns of lichen symbiont interactions at the largest geographic and taxonomic scales attempted to date. We analysed a total of 2356 algal internal transcribed spacer (ITS) region sequences collected from lichens representing ten mycobiont genera in Parmeliaceae, two genera in Lecanoraceae and 26 cultured Trebouxia strains. Algal ITS sequences were grouped into operational taxonomic units (OTUs); we attempted to validate the evolutionary independence of a subset of the inferred OTUs using chloroplast and mitochondrial loci. We explored the patterns of symbiont interactions in these lichens based on ecogeographic distributions and mycobiont taxonomy. We found high levels of undescribed diversity in Trebouxia, broad distributions across distinct ecoregions for many photobiont OTUs and varying levels of mycobiont selectivity and specificity towards the photobiont. Based on these results, we conclude that fungal specificity and selectivity for algal partners play a major role in determining lichen partnerships, potentially superseding ecology, at least at the ecogeographic scale investigated here. To facilitate effective communication and consistency across future studies, we propose a provisional naming system for Trebouxia photobionts and provide representative sequences for each OTU circumscribed in this study.     

Lichen acclimation to changing environments: Photobiont switching vs. climate‐specific uniqueness in Psora decipiens

Unraveling the complex relationship between lichen fungal and algal partners has been crucial in understanding lichen dispersal capacity, evolutionary processes, and responses in the face of environmental change. However, lichen symbiosis remains enigmatic, including the ability of a single fungal partner to associate with various algal partners. Psora decipiens is a characteristic lichen of biological soil crusts (BSCs), across semi‐arid, temperate, and alpine biomes, which are particularly susceptible to habitat loss and climate change. The high levels of morphological variation found across the range of Psora decipiens may contribute to its ability to withstand environmental change. To investigate Psora decipiens acclimation potential, individuals were transplanted between four climatically distinct sites across a European latitudinal gradient for 2 years. The effect of treatment was investigated through a morphological examination using light and SEM microscopy; 26S rDNA and rbcL gene analysis assessed site‐specific relationships and lichen acclimation through photobiont switching. Initial analysis revealed that many samples had lost their algal layers. Although new growth was often determined, the algae were frequently found to have died without evidence of a new photobiont being incorporated into the thallus. Mycobiont analysis investigated diversity and determined that new growth was a part of the transplant, thus, revealing that four distinct fungal clades, closely linked to site, exist. Additionally, P. decipiens was found to associate with the green algal genus Myrmecia, with only two genetically distinct clades between the four sites. Our investigation has suggested that P. decipiens cannot acclimate to the substantial climatic variability across its environmental range. Additionally, the different geographical areas are home to genetically distinct and unique populations. The variation found within the genotypic and morpho‐physiological traits of P. decipiens appears to have a climatic determinant, but this is not always reflected by the algal partner. Although photobiont switching occurs on an evolutionary scale, there is little evidence to suggest an active environmentally induced response. These results suggest that this species, and therefore, other lichen species, and BSC ecosystems themselves may be significantly vulnerable to climate change and habitat loss.     

Fungal tissue per se is stronger as a UV-B screen than secondary fungal extrolites in Lobaria pulmonaria

To test the hypotheses that (1) protective mycobiont tissues and/or (2) medullary UV-B-absorbing carbon-based secondary compounds (CBSCs) protect lichen photobionts against UV-B radiation, we quantified cortical UV-transmittance and ran a three-way factorial lab experiment with (1) three UV radiation regimes, (2) photobiont layers with/without a screening cortex, and (3) with natural/reduced CBSC-concentration. We used melanin-deficient Lobaria pulmonaria from shaded forests. Maximum photochemical efficiency of photosystem II (Fv/Fm) in photobionts inside thalli with natural CBSC-concentrations was not affected by any UV-regime, consistent with close to 0% measured cortical transmittance of wavelengths <325 nm. Exposing photobiont layers to direct radiation strongly aggravated photoinhibition (P < 0.001), as did an increase in UV-exposure (P < 0.001). The effect of CBSC-removal was weaker (yet significant at P = 0.001), mainly affecting exposed photobiont layers given short-wavelength UV radiation. Based on these findings, we conclude that the primary role of extrolites in L. pulmonaria is not to screen excess solar radiation.     

Populations of Lobaria pulmonaria (L.) Hoffm. in the Cansiglio Regional Forest (Veneto,Pre-Alps,north-east Italy): Distribution,diversity and conservation issues

Abstract

The distribution of the epiphytic macrolichen Lobaria pulmonaria (L.) Hoffm. was surveyed in the Regional Forest of Cansiglio, extending over 3,500 ha in the eastern part of the Veneto Pre-Alps (north-east Italy). Data on the main characteristics of the forest sites and on Lobaria trees were collected with the aim to evaluate the main ecological factors, related to forest composition and management, affecting the distribution of Lobaria pulmonaria. Lichen diversity was surveyed on 15 randomly selected Lobaria trees. A good correlation between macrolichens and the total number of species was found. The largest Lobaria populations are concentred in the north-eastern part of the forest, where mixed and multi-plane silver fir – beech formations prevail, and selective cutting is carried out. Our data has enabled us to develop some criteria for the identification of priority conservation sites for Lobaria pulmonaria and lichen diversity in the study area, improving the focus on biodiversity in the management of the forest.     

The impact of nitrogen deposition on photobiont‐mycobiont balance of epiphytic lichens in subtropical forests of central China

Excessive nitrogen (N) deposition can impact lichen diversity in forest ecosystems, and this is a particular situation in China. Here, we examined the N uptake, assimilation, and the impact of excessive N deposition on the symbiotic balance of dominant epiphytic lichens in the subtropical forests in the Mts. Shennongjia of central China. The results show that lichen species took up, assimilated and utilized more ammonium than nitrate in a species‐specific way, following the increase of N availability. The photobiont of the lichens decreased with the increase of N concentration following an initial increase, while the mycobiont response to the N addition was not apparent. Considerable variation in response to excessive N deposition exists among the lichen species. Usnea longissima could regulate its N uptake, resulting in a stable photobiont‐mycobiont ratio among N treatments. In contrast, the photobiont‐mycobiont ratio of other four lichens increased initially but decreased when N concentration exceeded a certain level, and N stress may have broken the balance between photobiont and mycobiont of these lichens. Our results suggest that most epiphytic lichens in subtropical forest of central China could uptake and assimilate more ammonium than nitrate and that the balance between photobiont and mycobiont of many epiphytic lichens might change with the increasing N deposition load, which could impact the lichen diversity of this forest ecosystem.     

Structural and functional processes during water vapour uptake and desiccation in selected lichens with green algal photobionts

Structural alterations of the photobiont and mycobiont cells of lichens have been related to CO₂-gas exchange during experiments involving water vapour uptake and desiccation of liquid-water-saturated thalli. Increasing water vapour uptake of air dry lichens led to a gradual unfolding of the photobiont cells in Lobaria pulmonaria, Pseudevernia furfuracea, Ramalina maciformis and Teloschistes lacunosus as studied by low-temperature scanning electron microscopy. The data indicated that globular, probably turgid, cells and also slightly infolded or even heavily collapsed cells contributed to positive net photosynthesis, which was reached after water vapour uptake by the four species studied. During desiccation of fully water-saturated thalli of L. pulmonaria, extrathalline water films gradually evaporated before maximum values of CO₂-gas exchange were measured and before photobiont cells started to shrivel. In contrast, in P. furfuracea the CO₂-gas exchange maximum was reached when a considerable percentage of photobiont cells had already collapsed and while other parts of the thalli were still covered with liquid water. Further desiccation led to cavitation of the cortical cells in both species, this occurring at water contents at which net photosynthesis was still positive.Abbreviations EF exoplasmic fracture face - LTSEM low-temperature scanning electron microscopy - NP net photosynthesis - PAR photosynthetic active radiation (400–700 nm) - PF plasmic fracture face We thank D. Pichier, P. Hatvani, H. Müller, Birmensdorf, and J.B. Winkler, Kiel, for technical assistance, and J. Innes, Birmensdorf, for correcting the English text. Stimulating discussion with R. Honegger (Institut für Pflanzenbiologie, Universität Zürich, Switzerland), L. Kappen (Botanisches Institut, Universität Kiel, Germany), T.G.A. Green (Department of Biological Sciences, Hamilton, New Zealand), and O.L. Lange (Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Germany) are gratefully acknowledged.     

Forest refugia revisited: nSSRs and cpDNA sequences support historical isolation in a wide‐spread African tree with high colonization capacity,Milicia excelsa (Moraceae)

The impact of the Pleistocene climate oscillations on the structure of biodiversity in tropical regions remains poorly understood. In this study, the forest refuge theory is examined at the molecular level in Milicia excelsa, a dioecious tree with a continuous range throughout tropical Africa. Eight nuclear microsatellites (nSSRs) and two sequences and one microsatellite from chloroplast DNA (cpDNA) showed a deep divide between samples from Benin and those from Lower Guinea. This suggests that these populations were isolated in separate geographical regions, probably for several glacial cycles of the Pleistocene, and that the nuclear gene pools were not homogenized despite M. excelsa’s wind‐pollination syndrome. The divide could also be related to seed dispersal patterns, which should be largely determined by the migration behaviour of M. excelsa’s main seed disperser, the frugivorous bat Eidolon helvum. Within Lower Guinea, a north–south divide, observed with both marker types despite weak genetic structure (nSSRs: F_ST = 0.035, cpDNA: G_ST = 0.506), suggested the existence of separate Pleistocene refugia in Cameroon and the Gabon/Congo region. We inferred a pollen‐to‐seed dispersal distance ratio of c. 1.8, consistent with wide‐ranging gene dispersal by both wind and bats. Simulations in an Approximate Bayesian Computation framework suggested low nSSR and cpDNA mutation rates, but imprecise estimates of other demographic parameters, probably due to a substantial gene flow between the Lower Guinean gene pools. The decline of genetic diversity detected in some Gabonese populations could be a consequence of the relatively recent establishment of a closed canopy forest, which could negatively affect M. excelsa’s reproductive system.     

Hitchhiking with forests: population genetics of the epiphytic lichen Lobaria pulmonaria in primeval and managed forests in southeastern Europe

Availability of suitable trees is a primary determinant of range contractions and expansions of epiphytic species. However, switches between carrier tree species may blur co‐phylogeographic patterns. We identified glacial refugia in southeastern Europe for the tree‐colonizing lichen Lobaria pulmonaria, studied the importance of primeval forest reserves for the conservation of genetically diverse populations and analyzed differences in spatial genetic structure between primeval and managed forests with fungus‐specific microsatellite markers. Populations belonged to either of two genepools or were admixed. Gene diversity was higher in primeval than in managed forests. At small distances up to 170 m, genotype diversity was lower in managed compared with primeval forests. We found significant associations between groups of tree species and two L. pulmonaria genepools, which may indicate “hitchhiking” of L. pulmonaria on forest communities during postglacial migration. Genepool B of L. pulmonaria was associated with European Beech (Fagus sylvatica) and we can hypothesize that genepool B survived the last glaciation associated within the refuge of European Beech on the Coastal and Central Dinarides. The allelic richness of genepool A was highest in the Alps, which is the evidence for a northern refuge of L. pulmonaria. Vicariant altitudinal distributions of the two genepools suggest intraspecific ecological differentiation.     

Distribution and dispersal ecology of Lobaria pulmonaria in the largest primeval beech forest of Europe

Occupancy and density of the epiphytic lichen L. pulmonaria were studied in the mountains of Uholka–Shyrokyi Luh (Ukraine), which include the largest primeval beech forest in Europe. The lichen occupancy was assessed on 314 plots laid out on a systematic grid. Additional data on population density were collected from 483 trees growing both, on and between these plots. The trees harbouring L. pulmonaria were distributed very sparsely within Uholka–Shyrokyi Luh, and occupy nearly 10 % of the studied perimeter. The generalized linear models showed that area of occupancy of L. pulmonaria was significantly influenced by altitude and canopy cover, whereas the species’ density was explained by habitat types and slope exposition. Population density is higher at the timberline than in the interior forest or on lowland meadows. We found a bimodal altitudinal distribution of L. pulmonaria, with maxima below and above 900 m a.s.l., where it prefers forest stands with loose or scattered canopy. The preferred position of L. pulmonaria on host tree trunks depends on stand density and allows the species to get the necessary level of insolation also in shaded sites where it grows higher up on the trunk than in open stands. While L. pulmonaria occupied trees with various diameters, juvenile individuals are more frequent on small trees, but mature lichen individuals are predominantly found on trees of average or large sizes. Fertile individuals require specific environmental conditions, which are available at intermediate altitudes, related with sheltered light, and horizontal terraces on slopes with eastern exposition. In general, the primeval beech forest of Uholka–Shyrokyi Luh harbours a high percentage of juvenile thalli of L. pulmonaria, which lack vegetative propagules. Mature individuals have a low frequency of fruit bodies and reproduce mainly with vegetative diaspores. We interpret this as an indication of a currently growing population of L. pulmonaria within the area. We hypothesize that transboundary air pollution has decreased the lichens’ population frequency and density and has altered the ratio of developmental stages in L. pulmonaria during earlier decades.     

Inter‐group variability in seed dispersal by white‐handed gibbons in mosaic forest

Seed dispersers, like white‐handed gibbons (Hylobates lar), can display wide inter‐group variability in response to distribution and abundance of resources in their habitat. In different home ranges, they can modify their movement patterns along with the shape and scale of seed shadow produced. However, the effect of inter‐group variability on the destination of dispersed seeds is still poorly explained. In this study, we evaluate how seed dispersal patterns of this arboreal territorial frugivore varies between two neighboring groups, one inhabiting high quality evergreen forest and one inhabiting low quality mosaic forest. We predicted a difference in seed dispersal distance between the two groups (longer in the poor quality forest). We hypothesized that this difference would be explained by differences in home range size, daily path length, and ranging tortuosity. After 6 months of data collection, the evergreen group had a smaller home range (12.4 ha) than the mosaic group (20.9 ha), significantly longer daily path lengths (1507 m vs. 1114 m respectively) and greater tortuosity (39.1 vs. 16.1 respectively). Using gut passage times and displacement rates, we estimated the median seed dispersal distance as 163 m for the evergreen group (high quality forest) and of 116 m for the mosaic group (low quality forest). This contradiction with our initial prediction can be explained in term of social context, resource distribution, and habitat quality. Our results indicate that gibbons are dispersers of seeds between habitats and that dispersal distances provided by gibbons are influenced by a range of factors, including habitat and social context.     

Remnants fragments preserve genetic diversity of the old forest lichen <Emphasis Type="Italic">Lobaria pulmonaria</Emphasis> in a fragmented Mediterranean mountain forest

Fragmentation represents a serious threat to biodiversity worldwide, however its effects on epiphytic organisms is still poorly understood. We study the effect of habitat fragmentation on the genetic population structure and diversity of the red-listed epiphytic lichen, Lobaria pulmonaria, in a Mediterranean forest landscape. We tested the relative importance of forest patch quality, matrix surrounding fragments and connectivity on the genetic variation within populations and the differentiation among them. A total of 855 thalli were sampled in 44 plots (400 m²) of 31 suitable forest fragments (beeches and oaks), in the Sierra de Ayllón in central Spain. Variables related to landscape attributes of the remnant forest patches such as size and connectivity and also the nature of the matrix or tree species had no significant effects on the genetic diversity of L. pulmonaria. Values of genetic diversity (Nei’s) were only affected by habitat quality estimated as the age patches. Most of the variation (76%) in all populations was observed at the smallest sampled unit (plots). Using multiple regression analysis, we found that habitat quality is more important in explaining the genetic structure of the L. pulmonaria populations than spatial distance. The relatively high level of genetic diversity of the species in old forest patches regardless of patch size indicates that habitat quality in a highly structured forest stand determines the population size and distribution pattern of this species and its associated lichen community. Thus, conservation programmes of Mediterranean mountain forests have to prioritize area and habitat quality of old forest patches.     

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.     

Contracting montane cloud forests: a case study of the Andean alder (Alnus acuminata) and associated fungi in the Yungas

Alnus acuminata is a keystone tree species in the Yungas forests and host to a wide range of fungal symbionts. While species distribution models (SDMs) are routinely used for plants and animals to study the effects of climate change on montane forest communities, employing SDMs in fungi has been hindered by the lack of data on their geographic distribution. The well‐known host specificity and common biogeographic history of A. acuminata and associated ectomycorrhizal (ECM) fungi provide an exceptional opportunity to model the potential habitat for this symbiotic assemblage and to predict possible climate‐driven changes in the future. We (1) modeled the present and future distributions of suitable habitats for A. acuminata; (2) characterized fungal communities in different altitudinal zones of the Yungas using DNA metabarcoding of soil and root samples; and (3) selected fungi that were significant indicators of Alnus. Fungal communities were strongly structured according to altitudinal forest types and the presence of Alnus. Fungal indicators of Alnus, particularly ECM and root endophytic fungi, were also detected in Alnus roots. Current and future (year 2050) habitat models developed for A. acuminata predict a 25–50 percent decrease in suitable area and an upslope shift of the suitable habitat by ca. 184–380 m, depending on the climate change scenario. Although A. acuminata is considered to be an effective disperser, recent studies suggest that Andean grasslands are remarkably resistant to forest invasion, and future range contraction for A. acuminata may be even more pronounced than predicted by our models.     

Effects of manganese on chlorophyll fluorescence in epiphytic cyano- and chlorolichens

Incubation with 10 mM MnCl₂ for 1 h decreased the effective quantum yield of photochemical energy conversion in photosystem 2 in the bipartite chlorolichen Hypogymnia physodes as well as in the bipartite cyanolichens Leptogium saturninum and Nephroma helveticum, but not in the tripartite lichen Lobaria pulmonaria. Among the bipartite species, Mn sensitivity increased in the order H. physodes < N. helveticum < L. saturninum. This equals the sequence heteromerous chlorolichen < heteromerous cyanolichen < homoiomerous (gelatinous) cyanolichen. MnCl₂ reduced non-photochemical quenching of chlorophyll fluorescence in the bipartite cyanolichens and in H. physodes; in the latter, however, this decrease was limited to light intensities above the adapted growth light intensity. Photochemical quenching was increased in H. physodes, but reduced in the bipartite cyanolichens. The results indicate that the bipartite cyanolichens L. saturninum and N. helveticum are even more sensitive to high Mn concentrations than the chlorolichen H. physodes, the low Mn tolerance of which has been already demonstrated. This agrees with results of field studies from western North America, where conifer bark under cyanolichens (including L. saturninum and N. helveticum) was found to contain less Mn than bark which only supported chlorolichens. The high sensitivity of the bipartite cyanolichens probably results from high sensitivity of the Nostoc photobiont. The high Mn tolerance of L. pulmonaria is probably not due to its being a tripartite lichen, but might be caused by high tolerance of the green-algal primary photobiont Dictyochloropsis, which is, however, not experimentally proven. The high Mn tolerance of the highly SO₂-sensitive L. pulmonaria shows that different mechanisms are responsible for Mn and SO₂ toxicity in lichens.