Terrestrial biodiversity along the Ross Sea coastline,Antarctica: lack of a latitudinal gradient and potential limits of bioclimatic modeling

Antarctica has several apparent advantages for the study of biodiversity change along latitudinal gradients including a relatively pristine environment and simple community structures. Published analyses for lichens and mosses show no apparent gradient in biodiversity along the western Ross Sea coast line, the longest ice-free area in Antarctica spanning 14° latitude. One suggestion is that the area remains poorly surveyed. Here, we combine available species lists from four sites along the coast with new own data from two additional sites [Taylor Valley (77°30′S) and Diamond Hill (79°S)]. We show a decline in total terrestrial biodiversity with latitude from Cape Hallett (72°S) to Diamond Hill. However, the southernmost site, the Queen Maud Mountains (84°S), is exceptional with almost the same diversity as Cape Hallett. A categorization of lichens according to their proposed ecology shows the proportion of tolerant species remains relatively constant. However, the absolute number of conformant species declines with latitude, again with a minimum at Diamond Hill. Similarity indices are low and not very different between sites with Diamond Hill being the exception with very few species. We suggest that terrestrial biodiversity best reflects microhabitat water availability rather than macroclimatic temperature changes and use climate data from Taylor Valley and Diamond Hill to support this suggestion. We propose that the importance of microhabitats and landscape location is one of several possible limitations to the application of bioclimatic modeling along the Ross sea coastline. In the absence of a definitive link between macroclimate and the biota, predicting the effects of climate changes will be more challenging.     

Multi‐scale patterns of moss and lichen richness on the Antarctic Peninsula

Mosses and lichens are the dominant macrophytes of the Antarctic terrestrial ecosystem. Using occurrence data from existing databases and additional published records, we analyzed patterns of moss and lichen species diversity on the Antarctic Peninsula at both a regional scale (1°latitudinal bands) and a local scale (52 and 56 individual snow‐ and ice‐free coastal areas for mosses and lichens, respectively) to test hypothesized relationships between species diversity and environmental factors, and to identify locations whose diversity may be particularly poorly represented by existing collections and online databases. We found significant heterogeneity in sampling frequency, number of records collected, and number of species found among analysis units at the two spatial scales, and estimated species richness using projected species accumulation curves to account for potential biases stemming from sample heterogeneity. Our estimates of moss and lichen richness for the entire Antarctic Peninsula region were within 20% of the total number of known species. Area, latitude, spatial isolation, mean summer temperature, and penguin colony size were considered as potential covariates of estimated species richness. Moss richness was correlated with isolation and latitude at the local scale, while lichen richness was correlated with summer mean temperature and, for 17 sites where penguins where present with <20 000 breeding pairs, penguin colony size. At the regional scale, moss richness was correlated with temperature and latitude. Lichen richness, by contrast, was not significantly correlated with any of the variables considered at the regional scale. With the exception of temperature, which explained 91% of the variation in regional moss diversity, explained variance was very low. Our results show that patterns of moss and lichen biodiversity are highly scale‐dependent and largely unexplained by the biogeographic variables found important in other systems.     

Global gradients in moss and vascular plant diversity

Knowledge on the distribution and hotspots of different taxon groups is indispensable for improving the state of biodiversity protection. Our aim was to determine if the relations between major environmental factors and species richness of two plant groups, mosses and vascular plants differ on a global scale. The dependence of species richness on environmental factors in 50 regions, covering 17 % of the global terrestrial territory, was analysed with SAS statistical software. Species richness of vascular plants increases significantly towards the equator, but for mosses the increase is not significant. Species richness of mosses and vascular plants are significantly positively correlated only in the near equator zone. Although there were similarities in the trends of mosses and vascular plant diversities at a global scale, their relations with some factors differ with distance from the equator. The effect of precipitation on species richness is similar for both plant groups, but coastline length has a significant positive influence only on moss richness, whereas species richness of vascular plants was related strongly to area and energy input. Therefore, effective conservation policy at both local and global scale demands consideration of all diversity drivers of different taxon groups.     

In situ monitoring of microclimate and metabolic activity in lichens from Antarctic extremes: a comparison between South Shetland Islands and the McMurdo Dry Valleys

Lichens are the dominant organisms in terrestrial Antarctic ecosystems and show a decline in species number, coverage, and growth rate from the maritime Antarctic (62°S) to the McMurdo Dry Valleys (78°S). While Livingston Island (maritime Antarctica) is a hot spot for lichen biodiversity, the McMurdo Dry Valleys (continental Antarctica) are known as one of the most extreme environments for life. Previous studies suggest the biodiversity gradient to be linked to water availability acting through length of active period, but no activity data are available for the Dry Valleys. The work presented here compares metabolic activity of lichens at Livingston Island and the Dry Valleys for 4½ months from continuous monitoring that involves concurrent measurements of chlorophyll fluorescence and microclimate. The latitudinal comparison involves two contrasting habitats for plant physiological activity and microclimate. Two species of the foliose genus Umbilicaria were monitored in both regions plus one sample of the crustose Caloplaca in the Dry Valleys. The results showed a very large difference in the duration of activity over the monitoring period, and this supports the different coverage, species abundance, and growth rates already reported for lichens between both regions. Despite this large difference in activity, and in habitat conditions, analysis of the activity behaviour of the two Umbilicaria species shows interesting common features, while the crustose Caloplaca had additional strategies to improve hydration. This offers one explanation for the abundance of crustose lichens inside the Valleys, indicating better adaptation strategies to a polar desert.     

Geothermal bryophyte habitats in the South Sandwich Islands,maritime Antarctic

Question: How does geothermal activity influence terrestrial plant colonization, species composition and community development in the Antarctic? Location: South Sandwich Islands, maritime Antarctic. Methods: Bryophytes were documented during a biological survey of the archipelago in January and February 1997. Particular attention was given to sites under current or recent influence of geothermal activity. Temperature profiles obtained across defined areas of activity on several islands were linked with the presence of specific bryophytes. Results: Greatest bryophyte richness was associated with geothermally influenced ground. Of 35 moss and nine liverwort species recorded, only four mosses were never associated with heated ground, while eight of the liverworts and 50% of the mosses were found only on actively or recently heated ground. Some species occur in unheated sites elsewhere in the maritime Antarctic, but were absent from such habitats on the South Sandwich Islands. Several species occurred in distinct zones around fumaroles. Maximum temperatures recorded within the upper 0.5 cm of the vegetation surface were 40 ‐ 47 °C, with only Campylopus introflexus tolerating such temperatures. Maximum temperatures 2.5 or 5 cm below the vegetation surface of this moss reached 75 °C. Other bryophytes regularly present in zoned vegetation included the mosses Dicranella hookeri, Sanionia georgico‐uncinata, Pohlia nutans and Notoligotrichum trichodon, and the liverworts Cryptochila grandiflora and Marchantia berteroana. Surface temperatures of 25 ‐ 35 °C and subsurface temperatures of 50 ‐ 60 °C were recorded in these species. Conclusions: These exceptional plant communities illustrate the transport of viable propagules into the Antarctic. Individually ephemeral in nature, the longer term existence of geothermal habitats on islands along the Scotia Arc may have provided refugia during periods of glacial expansion, facilitating subsequent recolonization of Antarctic terrestrial habitats.     

A survey of the terrestrial Tardigrada of the Vestfold Hills,Antarctica

A survey of the terrestrial tardigrades inhabiting growths of algae, lichens and mosses in the Vestfold Hills, Antarctica, was carried out at 11 and 35 sites during the austral summers of 1980 and 1982, respectively. In all, 24 species of plants were collected from which four genera and four species of Tardigrada were recovered. A key to the tardigrades of the area is presented. The distribution and associational patterns of the tardigrades are discussed in the context of other studies of antarctic Tardigrada.     

Relationship between avian range limits and plant transition zones in Maine

Aim To determine if vegetation complexity associated with transition zones may be a contributing factor affecting bird species distributions in Maine, USA, and in increased numbers of bird species at about 45° north latitude in northeastern North America. Location Maine, USA; North America north of Mexico. Methods We delineated the ranges within Maine (86,156 km²) of 186 bird species and 240 woody plants using literature and expert review. Maps showing species richness and numbers of range limits, at 324 km² resolution, were developed for woody plants and groups of breeding birds: forest specialists, forest generalists, and those that used barren and urban habitats, early successional areas, and wetlands or open water. Two plant transition zones for Maine were identified previously, with the north–south transition zone mapped across eastern North America. Patterns in bird distribution maps were compared to woody plant maps and to transition zones. Results When the distributions of forest specialists were compared to the north–south vegetation transition zone in Maine, they were spatially coincident, but were not for other groups. Forest specialists had more species with range limits in the state (61%) than generalists (13%) or any other group. At a continental‐scale, the vegetation transition zone within eastern North America agreed fairly well with the areas of highest bird richness. Main conclusions A bird transition zone occurs in Maine and across eastern North America, akin to and overlapping the vegetation transition zone. Seasonality is likely the primary source of the inverse gradient in bird richness in the eastern USA, as reported by others. However, vegetation structure and habitat selection at very broad spatial scales appear to contribute to the reversed gradient. North of the vegetation transition zone, forest structure is simpler and coniferous forests more dominant, and this may contribute to reduced bird species richness. However, the northern (> 49°) typical gradient in bird species richness has been related to many hypotheses, and several are likely involved in the genesis of the gradient.     

Life form and water source interact to determine active time and environment in cryptogams: an example from the maritime Antarctic

Antarctica, with its almost pristine conditions and relatively simple vegetation, offers excellent opportunities to investigate the influence of environmental factors on species performance, such information being crucial if the effects of possible climate change are to be understood. Antarctic vegetation is mainly cryptogamic. Cryptogams are poikilohydric and are only metabolically and photosynthetically active when hydrated. Activity patterns of the main life forms present, bryophytes (10 species, ecto- and endohydric), lichens (5 species) and phanerogams (2 species), were monitored for 21 days using chlorophyll a fluorescence as an indicator of metabolic activity and, therefore, of water regime at a mesic (hydration by meltwater) and a xeric (hydration by precipitation) site on Léonie Island/West Antarctic Peninsula (67°36′S). Length of activity depended mainly on site and form of hydration. Plants at the mesic site that were hydrated by meltwater were active for long periods, up to 100 % of the measurement period, whilst activity was much shorter at the xeric site where hydration was entirely by precipitation. There were also differences due to life form, with phanerogams and mesic bryophytes being most active and lichens generally much less so. The length of the active period for lichens was longer than in continental Antarctica but shorter than in the more northern Antarctic Peninsula. Light intensity when hydrated was positively related to the length of the active period. High activity species were strongly coupled to the incident light whilst low activity species were active under lower light levels and essentially uncoupled from incident light. Temperatures were little different between sites and also almost identical to temperatures, when active, for lichens in continental and peninsular Antarctica. Gradients in vegetation cover and growth rates across Antarctica are, therefore, not likely to be due to differences in temperature but more likely to the length of the hydrated (active) period. The strong effect on activity of the mode of hydration and the life form, plus the uncoupling from incident light for less active species, all make modelling of vegetation change with climate a more difficult exercise.     

Bryophyte and lichen diversity: A comparative study

Abstract We describe the regional species richness, variation in species richness and species turnover of bryophytes and lichens from 36 sites in lowland forests of southeastern Australia. The analyses subdivided the two major taxa into their constituent sub-groups: mosses, liverworts, and crustose, fruticose and foliose lichens. They also explored correlations between selected environmental variables and patterns of diversity. On a regional scale, there were 77 species of bryophytes and 69 species of lichens, giving a total of approximately one-third of the total number of vascular plant species in the region. Mean species richness was higher for lichens than bryophytes. Also, the two taxa were negatively correlated because lichens favoured dry sites and bryophytes favoured moist ones. Species turnover was greater for bryophytes than lichens, largely due to the distribution of liverwort species. Foliose lichens showed higher levels of turnover than crustose lichens. Multiple regression and canonical correspondence analysis showed that both taxa and all sub-groups responded to the same three variables: vascular plant cover, time since last fire and topographic position. Other variables, including time since logging and intensity of logging, explained little variation in bryophyte or lichen diversity. The data suggest that the strategies for the conservation of bryophyte and lichen biodiversity will be different, to reflect the different patterns of species richness and species turnover.     

Latitudinal patterns and regionalization of plant diversity along a 4270‐km gradient in continental Chile

According to the global latitudinal diversity gradient, a decrease in animal and plant species richness exists from the tropics towards higher latitudes. The aim of this study was to describe the latitudinal distribution patterns of Chilean continental flora and delineate biogeographic regions along a 4270‐km north–south gradient. We reviewed plant lists for each of the 39 parallels of continental Chile to build a database of the geographical distribution of vascular plant species comprising 184 families, 957 genera and 3787 species, which corresponded to 100%, 94.9% and 74.2% of the richness previously defined for Chile, respectively. Using this latitudinal presence–absence species matrix, we identified areas with high plant richness and endemism and performed a Cluster analysis using Jaccard index to delineate biogeographic regions. This study found that richness at family, genus and species levels follow a unimodal 4270‐km latitudinal distribution curve, with a concentration of richness in central Chile (31–42°S). The 37th parallel south (central Chile) presented the highest richness for all taxonomic levels and in specific zones the endemism (22–37°S) was especially high. This unimodal pattern contrasts the global latitudinal diversity gradient shown by other studies in the Northern hemisphere. Seven floristic regions were identified in this latitudinal gradient: tropical (18–22°S), north Mediterranean (23–28°S), central Mediterranean (29–32°S), south Mediterranean (33–37°S), north temperate (38–42°S), south temperate (43–52°S) and Austral (53–56°S). This regionalization coincides with previous bioclimatic classifications and illustrates the high heterogeneity of the biodiversity in Chile and the need for a reconsideration of governmental conservation strategies to protect this diversity throughout Chile.     

Distribution and floristics of moss- and lichen-dominated soil crusts in a patterned Callitris glaucophylla woodland in eastern Australia

The distribution and abundance of soil crust lichens and bryophytes was examined in a patterned Callitris glaucophylla woodland in eastern Australia. Twenty-one lichen species and 26 bryophyte species were collected within thirty quadrats along a sequence of runoff, interception and runoff zones. Crust cover was significantly greatest in the interception zones (79.0 %), followed by the runoff zones (24.0 %), and lowest in the groved, runon zones (6.6 %). Lichens and bryophytes were distributed across all geomorphic zones, and, although there were significantly more moss species in the interception zones (mean = 9.1) compared with either the runoff (4.2) or runon (3.2) zones, the number of lichen species did not vary between zones. Ordination of a reduced data set of 32 species revealed a separation of taxa into distinct groups corresponding to the three geomorphic zones. Canonical correspondence analysis (CCA) of the 32 species and thirteen environmental variables revealed that the most important factors associated with the distribution of species were sheet and scarp erosion, soil stability and coherence, litter cover and crust cover. Surface cracking, microtopography and plant cover were of intermediate importance. The CCA biplot revealed that the timbered runon zones (groves) were dominated by `shade-tolerant' mosses Fissidens vittatus and Barbula hornschuchiana, whilst the heavily eroded runoff zones supported sparse populations of `erosion tolerant' lichens (Endocarpon rogersii) and mosses (Bryum argenteum and Didymodon torquatus). Interception zones supported a rich suite of `crust forming' mosses and lichens capable of tolerating moderate inundation by overland flow. Two other groups of taxa were identified by this analysis: the `pioneer' group, comprising mainly nitrogen-fixing lichens which occupy the zone of active erosion at the lower edge of the groves, and the `opportunists' dominated by liverworts, occupying the shallow depressions or bays at the margins of the groves and the interception zones. This study confirms that the non-vascular lichens and bryophytes in these arid soil crusts, are, like the vascular plants, strongly patterned according to geomorphic zone, being most strongly associated with soil surface and erosional features.     

Assessing abundance and diversity patterns of soil microarthropod assemblages in northern Victoria Land (Antarctica)

This study aimed to: (1) assess differences between two quantitative sampling methods of soil microarthropods (visual census vs. stone washing) in ice-free areas located along a latitudinal gradient (from 72°37′S to 74°42′S) in northern Victoria Land (Antarctica); (2) furnish preliminary results on the abundance and diversity of mites and springtails in the studied areas. Visual census yielded reliable density estimates for adult collembolans and larger prostigmatic mites but did not detect small species. The study updates the distribution of several mites, including the southernmost record of an Oribatida species at global scale. Species composition was correlated with latitude but the uneven abundance distribution and local high beta-diversity probably reflect habitat fragmentation and population isolation. Under this circumstance nested sampling design should be usefully employed. Priorities and suitable methods for studying terrestrial microarthropod communities in continental Antarctica are discussed.     

Vegetation abundance on the Barton Peninsula,Antarctica: estimation from high-resolution satellite images

Polar biodiversity should be monitored as an indicator of climate change. Biodiversity is mainly observed by field survey although this is very limited in broad inaccessible polar regions. Satellite imagery may provide valuable data with less bias, although spatial, spectral, and temporal resolutions are limited for analyzing biodiversity. The present study has two objectives. The first is constructing a first-ever vegetation map of the entire Barton Peninsula, Antarctica. The second is developing a monitoring method for long-term variation of vegetation, based on satellite images. Dominant mosses and lichens are distributed in small and sparse patches, which are limited to analysis using high-resolution satellite images. A sub-pixel classification method, spectral mixture analysis, is applied to overcome limited spatial resolution. As a result, vegetation shows high abundance along the southeastern shore and low-to-medium abundance in the nearly snow-free inland area. Even though spatial patterns of vegetation were almost invariant over 6 years, there was interannual variation in abundance aspects because of meteorological conditions. Therefore, extensive and long-term monitoring is needed for aspects of distribution and abundance. The present results can be used to design field surveys and monitor long-term variation as elementary data.     

UAV-based classification of maritime Antarctic vegetation types using GEOBIA and random forest

Development of vegetation communities in areas of Antarctica without permanent ice cover emphasizes the need for effective remote sensing techniques for proper monitoring of local environmental changes. Detection and mapping of vegetation by image classification remains limited in the Antarctic environment due to the complexity of its surface cover, and the spatial heterogeneity and spectral homogeneity of cryptogamic vegetation. As ultra-high resolution aerial images allow a comprehensive analysis of vegetation, this study aims to identify different types of vegetation cover (i.e., algae, mosses, and lichens) in an ice-free area of  Hope Bay, on the northern tip of the Antarctic Peninsula. Using the geographic object-based image analysis (GEOBIA) approach, remote sensing data sets are tested in the random forest classifier in order to distinguish vegetation classes within vegetated areas. Because species of algae, mosses, and lichens may have similar spectral characteristics, subclasses are established. The results show that when only the mean values of green, red, and NIR bands are considered, the subclasses have low separability. Variations in accuracy and visual changes are identified according to the set of features used in the classification. Accuracy improves when multilayer information is used. A combination of spectral and morphometric products and by-products provides the best result for the detection and delineation of different types of vegetation, with an overall accuracy of 0.966 and a Kappa coefficient of 0.946. The method allowed for the identification of units primarily composed of algae, mosses, and lichens as well as differences in communities. This study demonstrates that ultra-high spatial resolution data can provide the necessary properties for the classification of vegetation in Maritime Antarctica, even in images obtained by sensors with low spectral resolution.     

中国地卷属地衣海拔分布分析

海拔是地衣多样性的重要影响因素。了解地衣的海拔分布格局是地衣多样性保护的基础。研究表明中国地卷属地衣的物种丰富度和个体丰富度沿海拔梯度呈单峰曲线,它们倾向于分布在受全球变暖影响较高的高海拔地区[（2,022±995）m],且具有较窄的海拔分布幅（约68%的物种分布于海拔为1,694－2,954m的地带）,因而对其进行保护生物学的研究已十分迫切。地卷属11种地衣具有不同的海拔分布规律,这些分布规律与各自分布的海拔区间有关。基于11物种的海拔分析支持Rapoport法则。全球暖化对4种地衣的潜在威胁尤其强烈,即：大陆地卷Peltigera continentalis、长孢地卷P. dolichospora、克氏地卷P. kristinssonii和小地卷P. venosa。     

Water as a resource,stress and disturbance shaping tundra vegetation

Water is crucial for plant productivity and survival as a fundamental resource, but water conditions can also cause physiological stress and mechanical disturbance to vegetation. However, these different influences of water on vegetation patterns have not been evaluated simultaneously. Here, we demonstrate the importance of three water aspects (spatial and temporal variation of soil moisture and fluvial disturbance) for three ecologically and evolutionary distinct taxonomical groups (vascular plants, mosses and lichens) in Fennoscandian mountain tundra. Fine‐scale plant occurrence data for 271 species were collected from 378 × 1 m² plots sampled over broad environmental gradients (water, temperature, radiation, soil pH, cryogenic processes and the dominant allelopathic plant species). While controlling all other key environmental variables, water in its different aspects proved to be a crucial environmental driver, acting on individual species and on community characteristics. The inclusion of the water variables significantly improved our models. In this high‐latitude system, the importance of spatial variability of water exceeds the importance of temperature for the fine‐scale distribution of species from the three taxonomical groups. We found differing responses to the three water variables between and within the taxonomical groups. Water as a resource was the most important water‐related variable in species distribution models across all taxonomical groups. Both water resource and disturbance were strongly related to vascular plant species richness, whereas for moss species richness, water resources had the highest influence. For lichen species richness, water disturbance was the most influential water‐related variable. These findings demonstrate that water variables are not only independent properties of tundra hydrology, but also that water is truly a multifaceted driver of vegetation patterns at high‐latitudes.     

Leben zwischen Eis und Felsen

Biological soil crusts in Antarctica: Life between ice and rocks Despite its adverse environmental conditions and geographical isolation, Antarctica is home to a rich vegetation of lichens, mosses, algae, fungi and bacteria. In the milder areas of the maritime and continental Antarctic, these pioneer species form widely visible biological soil crusts. In drier areas, they occur mainly within the outer rock and upper soil layers. Among the ecological adaptations that enable these species to survive Antarctic conditions, a good dehydration tolerance stands out. Almost nothing is known about the genetic diversity of most species. While some species probably originated in Antarctica, others are relatively late settlers.     

Vertical distribution of epiphytic lichens on Quercus laurina Humb. & Bonpl. in a remnant of cloud forest in the state of Veracruz,México

In the tropics, corticolous lichen richness and cover tend to increase from the trunk base to the top of the crown of trees. In this study we calculated the total beta diversity of the lichen community along a vertical gradient on Quercus laurina in Mexican cloud forest. By comparing the richness and cover of the lichens by zone, we show that foliose and fruticose lichens are a minor component of the total lichen species richness, but have a higher cover than the crustose lichens. Five zones were identified along each phorophyte (n = 15) with a diameter at breast height >40 cm. A total of 92 species were identified. Of these, 38% were found only in a single zone, 51% were shared between the different zones and 11% occurred across all zones. Species richness and cover increased from the lowest to the highest zones of the phorophytes. Dissimilarity in species composition between the zones could be explained by species replacement. An indicator species analysis revealed that only a few species, e.g. Hypotrachyna vexans, H. cf. sublaevigata and Ramalina cf. sinaloensis prefer a particular zone. The results show that the lichen community associated with Quercus laurina phorophytes is highly diverse and suggest that species richness and cover are related to the zone and the various growth forms.     

Benthic moss pillars in Antarctic lakes

Unique pillar-like colonies of aquatic mosses, rising from cyanobacterial and algal mats, have been discovered in some freshwater lakes in the vicinity of Syowa Station (69°00′S, 39°35′E), continental Antarctica. These moss pillars are about 40 cm in diameter and up to 60 cm high and occur at the lake bottoms mainly between 3 and 5 m depth. The primary component is a species of Leptobryum, a genus unknown in the continental Antarctic terrestrial bryoflora and as an aquatic genus elsewhere in the world. Bryum pseudotriquetrum is often an associated species. In longitudinal section the pillars reveal several whitish layers formed by mineral sediment and dead cyanobacteria. It is speculated that the biomass of aquatic mosses at the bottom of many Antarctic lakes is considerably greater than that previously estimated. Accepted: 11 April 1999