Greg R. Guerin

Leaf morphology shift linked to climate change

Climate change is driving adaptive shifts within species, but research on plants has been focused on phenology. Leaf morphology has demonstrated links with climate and varies within species along climate gradients. We predicted that, given within-species variation along a climate gradient, a morphological shift should have occurred over time due to climate change. We tested this prediction, taking advantage of latitudinal and altitudinal variations within the Adelaide Geosyncline region, South Australia, historical herbarium specimens (n = 255) and field sampling (n = 274). Leaf width in the study taxon, Dodonaea viscosa subsp. angustissima, was negatively correlated with latitude regionally, and leaf area was negatively correlated with altitude locally. Analysis of herbarium specimens revealed a 2 mm decrease in leaf width (total range 1–9 mm) over 127 years across the region. The results are consistent with a morphological response to contemporary climate change. We conclude that leaf width is linked to maximum temperature regionally (latitude gradient) and leaf area to minimum temperature locally (altitude gradient). These data indicate a morphological shift consistent with a direct response to climate change and could inform provenance selection for restoration with further investigation of the genetic basis and adaptive significance of observed variation.

The extent of forest in dryland biomes

Mapping the worlds dry forests The extent of forest area in dryland habitats, which occupy more than 40% of Earths land surface, is uncertain compared with that in other biomes. Bastin et al. provide a global estimate of forest extent in drylands, calculated from high-resolution satellite images covering more than 200,000 plots. Forests in drylands are much more extensive than previously reported and cover a total area similar to that of tropical rainforests or boreal forests. This increases estimates of global forest cover by at least 9%, a finding that will be important in estimating the terrestrial carbon sink. Science, this issue p. 635 Previously unreported forest areas in drylands increase the current estimate of global forest cover by at least 9%. Dryland biomes cover two-fifths of Earth’s land surface, but their forest area is poorly known. Here, we report an estimate of global forest extent in dryland biomes, based on analyzing more than 210,000 0.5-hectare sample plots through a photo-interpretation approach using large databases of satellite imagery at (i) very high spatial resolution and (ii) very high temporal resolution, which are available through the Google Earth platform. We show that in 2015, 1327 million hectares of drylands had more than 10% tree-cover, and 1079 million hectares comprised forest. Our estimate is 40 to 47% higher than previous estimates, corresponding to 467 million hectares of forest that have never been reported before. This increases current estimates of global forest cover by at least 9%.

Identifying centres of plant biodiversity in South Australia

We aimed to identify regional centres of plant biodiversity in South Australia, a sub-continental land area of 983,482 km2, by mapping a suite of metrics. Broad-brush conservation issues associated with the centres were mapped, specifically climate sensitivity, exposure to habitat fragmentation, introduced species and altered fire regimes. We compiled 727,417 plant species records from plot-based field surveys and herbarium records and mapped the following: species richness (all species; South Australian endemics; conservation-dependent species; introduced species); georeferenced weighted endemism, phylogenetic diversity, georeferenced phylogenetic endemism; and measures of beta diversity at local and state-wide scales. Associated conservation issues mapped were: climate sensitivity measured via ordination and non-linear modelling; habitat fragmentation represented by the proportion of remnant vegetation within a moving window; fire prone landscapes assessed using fire history records; invasive species assessed through diversity metrics, species distribution and literature. Compared to plots, herbarium data had higher spatial and taxonomic coverage but records were more biased towards major transport corridors. Beta diversity was influenced by sampling intensity and scale of comparison. We identified six centres of high plant biodiversity for South Australia: Western Kangaroo Island; Southern Mount Lofty Ranges; Anangu Pitjantjatjara Yankunytjatjara lands; Southern Flinders Ranges; Southern Eyre Peninsula; Lower South East. Species composition in the arid-mediterranean ecotone was the most climate sensitive. Fragmentation mapping highlighted the dichotomy between extensive land-use and high remnancy in the north and intensive land-use and low remnancy in the south. Invasive species were most species rich in agricultural areas close to population centres. Fire mapping revealed large variation in frequency across the state. Biodiversity scores were not always congruent between metrics or datasets, notably for categorical endemism to South Australia versus georeferenced weighted endemism, justifying diverse approaches and cautious interpretation. The study could be extended to high resolution assessments of biodiversity centres and cost:benefit analysis for interventions.

Nutlet morphology in Hemigenia R.Br. and Microcorys R.Br. (Lamiaceae)

Nutlets of Hemigenia R.Br. and Microcorys R.Br. were examined using SEM. Significant variation, mainly useful at the infrageneric level, was found in nutlet shape, nature of the attachment scar, nature of surface sculpturing, exocarp cell shape and sculpturing, and nature of the indumentum. Typical nutlets are ovoidal, strongly reticulate or rugose. The exocarp cells are isodiametric and convex to papillate. Also common are cylindrical nutlets, often with longitudinal ridging and papillate exocarp cells. Surface pitting and concave exocarp cells are rare. A cladistic analysis of nutlet characters suggests both Hemigenia and Microcorys are polyphyletic, and Microcorys paraphyletic with respect to Westringia Sm. Notwithstanding that, the infrageneric classification of Hemigenia was largely supported, while in Microcorys, there was support for sect. Hemigenioides, but sects Anisandra and Microcorys were not resolved as distinct.

Plant macrofossil evidence for the environment associated with the Riversleigh fauna

Fossil plant organs from probable Oligocene nodules at the Dunsinane Site at Riversleigh, Queensland, were studied. The deposit consists of a low diversity assemblage of reproductive and vegetative organs dominated by a single taxon of Casuarinaceae. The species of Casuarinaceae has affinities with Casuarina and Allocasuarina in having more four teeth per whorl on the photosynthetic branchlets and stomata hidden in deep furrows filled with trichomes, and as such represents the earliest known record of sub-family Cryptostomae. The species is described as Cryptostomiforma quinata gen. et sp. nov. A leaf species is assigned to Alectryon (Sapindaceae) on the basis of the anatomy of abaxial cuticular features. In particular, the morphology is indistinguishable from extant A. affinis, a species currently endemic to New Guinea. Organs with possible affinities to Rubus or Capparis were examined. The assemblage is interpreted as a possible vegetation mosaic, containing both deciduous vine thickets and sclerophyllous habitats. No evidence for the presence of rainforest was found and the fossils are not consistent with extensive lowland tropical rainforest.

Temperature influences stomatal density and maximum potential water loss through stomata of Dodonaea viscosa subsp. angustissima along a latitude gradient in southern Australia

It is well known that physical leaf traits influence leaf functions, and that these traits vary across environmental gradients. Stomata can influence leaf function, with changes in density and size affecting potential water loss, CO2 uptake, and also leaf cooling. Plasticity in stomatal traits occurs in response to environmental factors; however, identifying which factors have the greatest influence is often difficult. We investigated variation in leaf size, stomatal density and size, and potential water loss from open stomata (gwmax), in the Australian native shrub Dodonaea viscosa subsp. angustissima, across a range of environmental factors including temperature, rainfall and CO2. We used herbarium specimens collected across a latitudinal gradient, and also sampled along an elevation gradient in southern Australia. There were significant relationships between mean summer maximum temperature and stomatal density, and gwmax. We found no significant relationships between rainfall or CO2 and the leaf traits we studied. Increased stomatal density at warmer locations may result in an increase in the potential for transpiration, as a means for evaporative cooling. Alternatively, it may enable increased CO2 and nutrient uptake during the short, winter-growing season.

Leaf morphology shift: new data and analysis support climate link

Links between leaf morphology and temperature have been established at a range of ecological scales [[1][1],[2][2]]. Narrower leaves can lose heat without evapotranspiration during hot, dry summers [[3][3]]. We proposed that an observed decrease in leaf width in Dodonaea viscosa subsp. angustissima

Opportunities for Integrated Ecological Analysis across Inland Australia with Standardised Data from Ausplots Rangelands

Australian rangelands ecosystems cover 81% of the continent but are understudied and continental-scale research has been limited in part by a lack of precise data that are standardised between jurisdictions. We present a new dataset from AusPlots Rangelands that enables integrative rangelands analysis due to its geographic scope and standardised methodology. The method provides data on vegetation and soils, enabling comparison of a suite of metrics including fractional vegetation cover, basal area, and species richness, diversity, and composition. Cover estimates are robust and repeatable, allowing comparisons among environments and detection of modest change. The 442 field plots presented here span a rainfall gradient of 129–1437 mm Mean annual precipitation with varying seasonality. Vegetation measurements include vouchered vascular plant species, growth form, basal area, height, cover and substrate type from 1010 point intercepts as well as systematically recorded absences, which are useful for predictive modelling and validation of remote sensing applications. Leaf and soil samples are sampled for downstream chemical and genomic analysis. We overview the sampling of vegetation parameters and environments, applying the data to the question of how species abundance distributions (SADs) vary over climatic gradients, a key question for the influence of environmental change on ecosystem processes. We found linear relationships between SAD shape and rainfall within grassland and shrubland communities, indicating more uneven abundance in deserts and suggesting relative abundance may shift as a consequence of climate change, resulting in altered diversity and ecosystem function. The standardised data of AusPlots enables such analyses at large spatial scales, and the testing of predictions through time with longitudinal sampling. In future, the AusPlots field program will be directed towards improving coverage of space, under-represented environments, vegetation types and fauna and, increasingly, re-sampling of established plots. Providing up-to-date data access methods to enhance re-use is also a priority.

Bioclimatic transect networks: powerful observatories of ecological change

Abstract Transects that traverse substantial climate gradients are important tools for climate change research and allow questions on the extent to which phenotypic variation associates with climate, the link between climate and species distributions, and variation in sensitivity to climate change among biomes to be addressed. However, the potential limitations of individual transect studies have recently been highlighted. Here, we argue that replicating and networking transects, along with the introduction of experimental treatments, addresses these concerns. Transect networks provide cost‐effective and robust insights into ecological and evolutionary adaptation and improve forecasting of ecosystem change. We draw on the experience and research facilitated by the Australian Transect Network to demonstrate our case, with examples, to clarify how population‐ and community‐level studies can be integrated with observations from multiple transects, manipulative experiments, genomics, and ecological modeling to gain novel insights into how species and systems respond to climate change. This integration can provide a spatiotemporal understanding of past and future climate‐induced changes, which will inform effective management actions for promoting biodiversity resilience.

‘Sum of inverse range-sizes’ (SIR), a biodiversity metric with many names and interpretations

Abstract Range restriction is an important measure of species rarity that is also interpreted as endemism. A simple biodiversity metric, the sum of inverse range-sizes (‘SIR’) for species within a sampling unit is useful for conservation planning but has multiple names and applications: for example, to highlight areas of high biodiversity and biological uniqueness (the hotspots problem, e.g. ‘weighted endemism’) and as a range proportion-explicit metric for calculating complementarity in reserve selection (the representation problem, e.g. ‘rarity-weighted richness’). This paper outlines the development, implementation and duplication of SIR. We propose that terminology for equivalent metrics can be unified if:- ‘SIR’ refers to them generally; those based on site or grid cell occupancy, or area of occupancy, are referred to specifically as ‘range-rarity richness’); while those aimed at measuring endemism based on extent of occurrence are referred to specifically as ‘georeferenced weighted endemism’. The phylogenetic equivalents would then be ‘phylogenetic range-rarity’ and ‘georeferenced phylogenetic endemism’, respectively.