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In semiarid regions, decreasing rainfall presents a challenge to perennial seedlings that must reach sufficient size to survive the first year’s seasonal drought. Attaining a large storage organ size has been hypothesized to enhance drought resilience in geophytes, but building larger storage organs requires faster growth, but paradoxically, some traits that confer faster growth are highly sensitive to drought. We examined whether tuber size confers greater drought resilience in seedlings of four closely related geophytic species ofPelargonium.

We imposed two drought treatments when seedlings were 2 months old: chronic low water and acute water restriction for 10 days. Plants in the acute dry‐down treatment were then rewatered at control levels. We compared morphological and ecophysiological traits at 2, 3, and 6 months of age and used mixed‐effects models to identify traits determining tuber biomass at dormancy.

Despite a 10‐fold variation in size, species had similar physiological trait values under well‐watered conditions. Chronic and acute droughts negatively affected tuber size at the end of the season, but only in the two species with large tubers. Chronic drought did not affect physiological traits of any species, but in response to acute drought, larger species showed reduced photosynthetic performance. Canopy area was the best predictor of final tuber biomass.

Contradictory to the hypothesis that large tubers provide greater drought resiliency, smallPelargoniumseedlings actually had higher drought tolerance, although at the expense of more vigorous growth compared to species with larger tubers under well‐watered conditions.

The functional significance of leaf margins has long been debated. In this study, we explore influences of climate, leaf lobing, woodiness, and shared evolutionary history on two leaf margin traits within the genusPelargonium.

Leaves from 454 populations ofPelargonium(161 species) were collected in the Greater Cape Floristic Region and scored for tooth presence/absence and degree of lobing. Tooth density (number of teeth per interior perimeter distance) was calculated for a subset of these. We compared five hypotheses to explain tooth presence and density using mixed effect models.

Tooth presence/absence was best predicted by the interaction of leaf lobing and mean annual temperature (MAT), but often in patterns opposite those previously reported: species were more likely to be toothed with warmer temperatures, particularly for unlobed and highly lobed leaves. In contrast, tooth density was best predicted by the interaction ofMATand the season of most rain; density declines with temperature as consistent with expectations, but only in winter‐rain dominated areas. Woody and nonwoody species withinPelargoniumhave similar associations between tooth presence/absence andMAT, contrary to the expectation that patterns within nonwoody species would be insignificant.

We concludePelargoniumleaf margins show predictable responses to climate, but these responses are complex and can contradict those found for global patterns across plant communities.

With plant biodiversity under global threat, there is an urgent need to monitor the spatial distribution of multiple axes of biodiversity. Remote sensing is a critical tool in this endeavour. One remote sensing approach for detecting biodiversity is based on the hypothesis that the spectral diversity of plant communities is a surrogate of multiple dimensions of biodiversity. We investigated the generality of this ‘surrogacy’ for spectral, species, functional and phylogenetic diversity across 1,267 plots in the Greater Cape Floristic Region (GCFR), a hyper‐diverse region comprising several biomes and two adjacent global biodiversity hotspots.

The GCFR centred in south‐western and western South Africa.

All data were collected between 1978–2014.

Vascular plants within the GCFR.

Spectral diversity was calculated using leaf reflectance spectra (450–950 nm) and was related to other dimensions of biodiversity via linear models. The accuracy of different spectral diversity metrics was compared using 10‐fold cross‐validation.

We found that a distance‐based spectral diversity metric was a robust predictor of species, functional and phylogenetic biodiversity. This result serves as a proof‐of‐concept that spectral diversity is a potential surrogate of biodiversity across a hyper‐diverse biogeographic region. While our results support the generality of spectral diversity as a biodiversity surrogate, we also find that relationships vary between different geographic subregions and biomes, suggesting that differences in broad‐scale community composition can affect these relationships.

Spectral diversity was shown to be a robust surrogate of multiple dimensions of biodiversity across biomes and a widely varying biogeographic region. We also extend these surrogacy relationships to ecological redundancy to demonstrate the potential for additional insights into community structure based on spectral reflectance.