Assembly of functional diversity in an oceanic island flora

Barbosa, Martha Paola Barajas; Craven, Dylan; Weigelt, Patrick; Denelle, Pierre; Otto, Rüdiger; Dı́az, Sandra; Price, Jonathan P.; Fernández‐Palacios, José María; Kreft, Holger

doi:10.1101/2022.03.04.482684

Cited by 9 publications

(15 citation statements)

References 65 publications

(67 reference statements)

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“…speciation is non-adaptive on the Canary Islands as endemic species only marginally increase functional diversity. A recent study on Tenerife concurs with our results by showing that cladogenetic plant species are tightly packed in trait space(Barajas-Barbosa et al, 2022). A relaxed competition on oceanic islands may allow genetic drift to become dominant over adaptive processes(Stuessy et al, 2006).…”

supporting

confidence: 91%

“…Indeed, the Canary Islands are a hotspot of insular woody species and succulent plants (Irl et al, 2020;Barajas-Barbosa et al, 2022;Zizka et al, 2022), which suggests that a large proportion of the Canary Islands flora could be resilient to the predicted climatic changes. Nonetheless, with ongoing climate change, a net loss of species with unique functions seems inevitable, leading to a functional homogenisation and a possible deterioration of ecosystem stability (Olden et al, 2004;Clavel et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

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Functional island biogeography and functional ecology of the Canary Islands flora

Hanz¹

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Oceanic islands only comprise a small amount of the Earth’s land area but harbour a disproportionate amount of global biodiversity. This vast diversity is not only reflected in the taxonomic uniqueness of island biota but also in the remarkable evolution of functional traits. Functional traits, i.e. measurable characteristics that strongly influence the fitness of species, determine how a species responds to its environment and can help to gain more insights into the biogeographical, ecological and evolutionary processes that have shaped island biodiversity. However, research in island biogeography has primarily focused on species richness, and knowledge of functional trait patterns on oceanic islands is scarce. Hence, in this dissertation, I have explored how trait-based approaches can increase our understanding of how biodiversity on oceanic islands assembles and how it is driven by the environment. The Canary Islands (Spain) are a particularly suitable model system to investigate patterns and drivers of biodiversity. The archipelago is characterised by a high variation in environmental heterogeneity and inhabits a unique and well-described native flora. Therefore, I have investigated five principal research questions using the flora (Spermatophytes) of the Canary Islands as a study object. First, I have analysed how climate and biogeography shape the assembly of the Canary Islands flora using a novel trait-based approach. Second, the question of whether rare climates link to functional trait distinctiveness in the native Canary Islands flora was addressed. Third, I have examined how intraspecific trait variation is represented in the native flora of oceanic islands focusing on the succulent scrub of La Palma (Canary Islands). Fourth, this dissertation investigated whether scientific floras can be reliable sources for trait data of plants native to oceanic islands. Finally, I have explored how climate change may impact the native Canary Islands flora by analysing possible climate change-induced shifts in plant species distribution and plant traits. The results of my dissertation expand the understanding of the importance of biogeography and the environment in determining the functional composition of island floras. I have assessed that traits of endemic plant species did not expand the functional trait space of the Canary Islands but were packed with the ones of non-endemic species. This result hints at a trait convergence in endemic species, possibly driven by non-adaptive speciation processes. Moreover, I have evidenced that humidity is a critical driver of functional diversity in native plant assemblages and particularly leads to a high trait convergence in arid environments via environmental filtering. In contrast, alien species have expanded the Canary Islands flora’s functional trait space. I further have shown that in contrast to native species assemblages, alien species assemblages are characterised by an increasing functional diversity with increasing aridity. This contrasting pattern of functional diversity could pose a potential risk to the native flora of the Canary Islands as a low functional diversity is expected to reduce the resilience of species assemblages to the establishment of more functionally diverse alien plant species. However, in this dissertation, I also have revealed that endemic plant species on the Canary Islands show a high intraspecific variation in arid environments, possibly as an adaptation to environmental stress. Intraspecific variation could help endemic plant species have a competitive advantage over alien species and be more resilient to environmental changes. Furthermore, in this dissertation, I have shown that scientific floras and taxonomic monographs could be used to gain information on quantitative functional traits of plants native to oceanic islands. This finding is particularly relevant for advances in trait-based research, as coverage of trait data for oceanic island floras is extremely poor in global trait databases. Hence, for some of the studies included in this dissertation, trait data were retrieved from scientific floras and taxonomic monographs and used to answer novel scientific research questions. Thus, I have used trait data from the literature to analyse the effect of climate change on the range size of plants native to the Canary Islands. Identifying plant species of particular conservation concern is critical on oceanic islands as many island species have limited distributions and small population sizes, and their niche tracking is impeded by insularity. I have revealed that single-island endemic plants gain less and lose more climatically suitable areas than archipelago endemic and non-endemic native plants due to a climate change-induced decrease in precipitation until 2100...

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confidence: 91%

Section: Discussionmentioning

confidence: 99%

Functional island biogeography and functional ecology of the Canary Islands flora

Hanz¹

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“…However, insular woody and succulent species may have an advantage in a climate that is warmer and drier than today on the Canary Islands. Indeed, the Canary Islands are a hotspot of insular woody species and succulent plants (Barajas‐Barbosa et al, 2022; Irl et al, 2020; Zizka et al, 2022), which suggests that a large proportion of the Canary Islands flora could be able to cope with the predicted climatic changes. Nonetheless, with ongoing climate change, a net loss of species with unique functions seems inevitable, leading to functional homogenisation and impoverishment, and a possible deterioration of ecosystem stability.…”

Section: Discussionmentioning

confidence: 99%

Effects of climate change on the distribution of plant species and plant functional strategies on the Canary Islands

Hanz

Cutts

Barbosa

et al. 2023

Diversity and Distributions

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AimOceanic islands possess unique floras with high proportions of endemic species. Island floras are expected to be severely affected by changing climatic conditions as species on islands have limited distribution ranges and small population sizes and face the constraints of insularity to track their climatic niches. We aimed to assess how ongoing climate change affects the range sizes of oceanic island plants, identifying species of particular conservation concern.LocationCanary Islands, Spain.MethodsWe combined species occurrence data from single‐island endemic, archipelago endemic and nonendemic native plant species of the Canary Islands with data on current and future climatic conditions. Bayesian Additive Regression Trees were used to assess the effect of climate change on species distributions; 71% (n = 502 species) of the native Canary Island species had models deemed good enough. To further assess how climate change affects plant functional strategies, we collected data on woodiness and succulence.ResultsSingle‐island endemic species were projected to lose a greater proportion of their climatically suitable area (x ̃ = −0.36) than archipelago endemics (x ̃ = −0.28) or nonendemic native species (x ̃ = −0.26), especially on Lanzarote and Fuerteventura, which are expected to experience less annual precipitation in the future. Moreover, herbaceous single‐island endemics were projected to gain less and lose more climatically suitable area than insular woody single‐island endemics. By contrast, we found that succulent single‐island endemics and nonendemic natives gain more and lose less climatically suitable area.Main ConclusionsWhile all native species are of conservation importance, we emphasise single‐island endemic species not characterised by functional strategies associated with water use efficiency. Our results are particularly critical for other oceanic island floras that are not constituted by such a vast diversity of insular woody species as the Canary Islands.

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“…Our main goal was to study the relationship between multiple diversity facets and forest productivity in two areas with similar climates but contrasting biogeographic contexts. We selected the Canary Islands archipelago (hereafter ‘the Canaries’) as our focal oceanic archipelago because its flora has been extensively studied (Acebes‐Ginovés et al., 2010; Barajas Barbosa et al., 2023) and it has broad environmental gradients in elevation and aridity (Ashmole & Ashmole, 2016; del Arco Aguilar & Rodríguez Delgado, 2018). Located in the Atlantic Ocean off the northwestern tip of Africa, the Canaries are an archipelago of volcanic origin formed progressively starting around 60 Ma (Troll & Carracedo, 2016).…”

Section: Methodsmentioning

confidence: 99%

“…Specifically, we expected (1) positive multifaceted biodiversity‐productivity relationships due to complementarity acting on both island and mainland forests, with phylogenetic diversity having a stronger influence on productivity than taxonomic or functional diversity as it can estimate the functional trait space of a community and also reflect species interactions (Srivastava et al., 2012), and phylogenetic diversity has been found to promote ecosystem functions and stability (Cadotte et al., 2012; van der Plas, 2019; Venail et al., 2015). We hypothesised that the magnitude of multifaceted biodiversity‐productivity relationships differ between biogeographic contexts, with stronger relationships on islands because a large proportion of island biota evolved in these ecosystems and therefore developed specific traits to more efficiently use limited resources or to persist in harsh environments (Barajas Barbosa et al., 2023; Emerson & Gillespie, 2008); (2) environmental conditions, that is climate and soil properties, influence productivity on island and mainland forests, as bioclimatic variables and soil nutrients have been shown to strongly influence plant diversity (Kreft & Jetz, 2007; Lambers et al., 2011) and productivity (following the species‐energy hypothesis); (3) the number of individuals positively influences productivity on island and mainland forests, as a higher number of individuals is expected to host a more biodiverse community (following the more‐individuals hypothesis), which subsequently is expected to yield higher productivity (Gaston, 2000; Srivastava & Lawton, 1998); and (4) non‐native species potentially influence productivity in both island and mainland forests, with the effect being stronger and positive on islands as non‐native species likely perform different functions than native species (Rothstein et al., 2004; Vitousek et al., 1996). However, as the Canary Islands forests may not have been impacted by non‐native species as extensively as other oceanic islands (Fernández‐Palacios et al., 2023), the influence of non‐native species on ecosystem functioning may be similar to that of mainland forests.…”

Section: Introductionmentioning

confidence: 99%

Biogeographic context mediates multifaceted diversity‐productivity relationships in island and mainland forests

Tolmos,

Guerrero‐Ramirez,

Ameztegui

et al. 2024

Journal of Ecology

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Biotic and abiotic conditions have been found to strongly influence how biodiversity affects ecosystem functioning in forests. This context dependency of biodiversity‐productivity relationships in real‐world ecosystems may be shaped by the biogeographic context via deep‐time processes acting on the size and composition of the species pool such as dispersal limitation, environmental filtering, speciation and invasibility. However, the role of the biogeographic context in shaping multifaceted biodiversity and forest productivity relationships remains uncertain. Using data from the Spanish National Forest Inventory in climatically similar forests on the Canary Islands (637 plots) and mainland Spain (1434 plots), we investigate the extent to which above‐ground productivity is determined by ecological and evolutionary processes associated with the biogeographic context. We used structural equation models to test the drivers of above‐ground productivity in both contexts, that operate via multifaceted tree diversity (taxonomic, phylogenetic, and functional diversity) or alternative mechanisms, that is environmental conditions, non‐native species, and the number of trees. Our results show that mainland and island forests exhibit similar levels of productivity, yet island forests display overall lower multifaceted diversity. We found that the number of trees increased multifaceted diversity and also increased productivity directly and via their effects on phylogenetic diversity in both mainland and island forests. Further, non‐native species increased productivity in island forests. Synthesis: Our results suggest that multifaceted diversity, by capturing the diversity of evolutionary history, contributes to elucidating diversity‐productivity relationships in mainland and island forests that could not be detected by taxonomic diversity alone. By filling empty niches in island forests, we find that non‐native species are fundamentally altering ecosystem functioning on islands and thus, reveal how biogeographic context can shape biodiversity‐productivity relationships.

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Assembly of functional diversity in an oceanic island flora

Cited by 9 publications

References 65 publications

Functional island biogeography and functional ecology of the Canary Islands flora

Functional island biogeography and functional ecology of the Canary Islands flora

Effects of climate change on the distribution of plant species and plant functional strategies on the Canary Islands

Biogeographic context mediates multifaceted diversity‐productivity relationships in island and mainland forests

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