Biology subjects

Martins, I. S.

Publications and source records attributed to Martins, I. S..

8 recordsLinked to original sources

bioRxiv2026

Short and long-term consequences of Habitat Transformation for Biodiversity

Humans have dramatically altered the Earths surface and the distributions of species, but coherent patterns distinguishing cause from effect are hard to discern. Community composition and ecosystem function can change as rapidly as local land-use, and we lack robust principles to understand the outcomes of these changes. This hampers assessments of ecosystem collapse or robustness. Here we create theoretical ecosystems using a community assembly framework in which we manipulate environmental filtering via both the local land-use and species traits. This isolates the impacts of environmental filtering into land-use, land-use change, and species trait diversity, allowing us to extract clear patterns and relationships. First, we identify the paradox of maladaptation. We find that better land-use adaptation reduces species richness in the habitat but increases species abundance and ecosystem complexity. Increasing diversity amongst species traits reduces species richness via a similar mechanism. Additionally, whilst over long time scales there is very little effect of land-use change, on very short time scales there is a predominantly negative effect on richness. Together, this highlights the need for careful facilitation and management of land-use change in the face of an ever-changing world. Author SummaryHumans have dramatically altered the Earths surface, primarily through land-use change and changing where species are and where they can go. This has resulted in extinctions, immigration, and, most of all, variation in where species end up. Here, we use simulations to compare how habitat, habitat change, and species adaptations create variation in outcomes due to land-use change. First, we show that while adaptation is good for individual species, it also reduces the overall diversity (number of species) of the ecosystem; similarly, well-adapted species out-perform and exclude less well-adapted species, also lowering the resulting diversity of the ecosystem. Secondly, we find that habitat change has different short- and long-term consequences. Habitat change can create dramatic declines on short time scales due to the different pressures experienced by species based on which species they eat (trophic level). But, on long time scales it has very little effect on diversity, as communities acquire new species adapted to the new conditions. We conclude that short-term declines in diversity due to recent or ongoing habitat change could be eased by helping well-adapted species to immigrate to form ecological communities in the new environment.

ecology↗

bioRxiv2023

Disentangling non-random structure from random placement when estimating β-diversity through space or time

There is considerable interest in understanding patterns of {beta}-diversity that measure the amount of change in species composition through space or time. Most hypotheses for {beta}-diversity evoke nonrandom processes that generate spatial and temporal within species aggregation; however, {beta}-diversity can also be driven by random sampling processes. Here, we describe a framework based on rarefaction curves that quantifies the non-random contribution of species compositional differences across samples to {beta}-diversity. We isolate the effect of within-species spatial or temporal aggregation on beta-diversity using a coverage standardized metric of {beta}-diversity ({beta}C). We demonstrate the utility of our framework using simulations and an empirical case study examining variation in avian species composition through space and time in engineered versus natural riparian areas. The primary strengths of our approach are that it provides an intuitive visual null model for expected patterns of biodiversity under random sampling that allows integrating analyses across -, {gamma}-, and {beta}-scales. Importantly, the method can accommodate comparisons between communities with different species pool sizes, and can be used to examine species turnover both within and between meta-communities. Open Research statement: all code and data used in this manuscript are available at the following link: https://github.com/MoBiodiv/beta_concept

ecology↗

bioRxiv2023

Widespread reductions in body size are paired with stable assemblage biomass.

Biotic responses to global change include directional shifts in organismal traits. Body size, an integrative trait that determines demographic rates and ecosystem functions, is often thought to be shrinking in the Anthropocene. Here, we assess the prevalence of body size change in six taxon groups across 5,032 assemblage time-series spanning 1960-2020. Using the Price equation to partition this change into within-species body size versus compositional changes, we detect prevailing decreases in body size through time. Change in assemblage composition contributes more to body size changes than within-species trends, but both components show substantial variation in magnitude and direction. The biomass of assemblages remains remarkably stable as decreases in body size trade-off with increases in abundance. One-Sentence SummaryVariable within-species and compositional trends combine into shrinking body size, abundance increases and stable biomass.

ecology↗

bioRxiv2022

Synthesis reveals biotic homogenisation and differentiation are both common

It is commonly thought that the biodiversity crisis includes widespread decreases in the uniqueness of different sites in a landscape (biotic homogenization). Using a typology relating homogenization and differentiation to local and regional diversity changes, we synthesize patterns across 283 metacommunities surveyed for 10-91 years, and 54 species checklists (13-500+ years). On average, there is a 0.2% increase in species shared among communities/year (i.e., weak homogenization), but across data sets, differentiation frequently occurs, with no statistically significant change being most common. Local (not regional) diversity frequently underlies composition change, and homogenization is strongly associated with checklist data that have longer durations and large spatial scales. Conservation and management can benefit from the multiscale perspective used here as it disentangles the implications of both the differentiation and homogenization currently unfolding. One-Sentence SummaryBiotic homogenization is most prevalent at large temporal and spatial scales.

ecology↗

bioRxiv2021

Local biodiversity change reflects interactions among changing abundance, evenness and richness

Biodiversity metrics often integrate data on the presence and abundance of multiple species. Yet understanding covariation of changes to the numbers of individuals, the evenness of species relative abundances, and the total number of species remains limited. Using individual-based rarefaction curves, we introduce a conceptual framework to understand how expected positive relationships among changes in abundance, evenness and richness arise, and how they can break down. We then examined interdependencies between changes in abundance, evenness and richness in more than 1100 assemblages sampled either through time or across space. As predicted, richness changes were greatest when abundance and evenness changed in the same direction, and countervailing changes in abundance and evenness acted to constrain the magnitude of changes in species richness. Site-to-site changes in abundance, evenness, and richness were often decoupled, and pairwise relationships between changes in these components across assemblages were weak. In contrast, changes in species richness and relative abundance were strongly correlated for assemblages varying through time. Temporal changes in local biodiversity showed greater inertia and stronger relationships between the component changes when compared to site-to-site variation. Local variation in assemblage diversity was rarely due to a passive sample from a more or less static species abundance distribution. Instead, changing species relative abundances often dominated local variation in diversity. Moreover, how changing relative abundances combined with changes to total abundance frequently determined the magnitude of richness changes. Embracing the interdependencies between changing abundance, evenness and richness can provide new information for better understanding biodiversity change in the Anthropocene.

ecology↗

bioRxiv2021

A millennium of increasing ecosystem diversity until the mid-20th century

Land-use change is widely regarded as a simplifying and homogenising force in nature. In contrast, analysing global land-use reconstructions from the 10th to 20th centuries, we found progressive increases in the number, evenness, and diversity of ecosystems (including human-modified land-use types) across the globe. Ecosystem diversity increased more rapidly after [~]1700CE, then slowed or partially reversed (depending on the metric) following the mid-20th century acceleration of human impacts. Differentiation also generally increased across space, with homogenization only evident in the presence-absence analysis of ecosystem types at the global scale. Our results suggest that human land-use changes have primarily driven increases in ecosystem diversity over the last millennium.

ecology↗

bioRxiv2018

A protocol for an intercomparison of biodiversity and ecosystem services models using harmonized land-use and climate scenarios

Abstract.To support the assessments of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), the IPBES Expert Group on Scenarios and Models is carrying out an intercomparison of biodiversity and ecosystem services models using harmonized scenarios (BES-SIM). The goals of BES-SIM are (1) to project the global impacts of land use and climate change on biodiversity and ecosystem services (i.e. natures contributions to people) over the coming decades, compared to the 20th century, using a set of common metrics at multiple scales, and (2) to identify model uncertainties and research gaps through the comparisons of projected biodiversity and ecosystem services across models. BES-SIM uses three scenarios combining specific Shared Socio-economic Pathways (SSPs) and Representative Concentration Pathways (RCPs) to explore a wide range of land-use change and climate change futures. This paper describes the rationale for scenarios selection, the process of harmonizing input data for land use, based on the second phase of the Land Use Harmonization Project (LUH2), and climate, the biodiversity and ecosystem service models used, the core simulations carried out, the harmonization of the model output metrics, and the treatment of uncertainty. The results of this collaborative modelling project will support the ongoing global assessment of IPBES, strengthen ties between IPBES and the Intergovernmental Panel on Climate Change (IPCC) scenarios and modelling processes, advise the Convention on Biological Diversity (CBD) on its development of a post-2020 strategic plans and conservation goals, and inform the development of a new generation of nature-centred scenarios.

ecology↗

bioRxiv2016

Extinction rate has a complex and non-linear relationship with area

Aim.Biodiversity loss, measured as count of extinction events, is a key component of biodiversity change, and can significantly impact ecosystem services. However, estimation of the loss has focused mostly on per-species extinction rates measured over limited numbers of spatial scales, with no theory linking small-scale extirpations with global extinctions. Here we provide such link by introducing the relationship between area and per-species probability of extinction (PxAR) and between area and count of realized extinction events in that area (NxAR). We show theoretical and empirical forms of these relationships, and we discuss their role in perception and estimation of the current extinction crisis.\n\nLocationUSA, Europe, Czech Republic, Barro Colorado Island\n\nMethodsWe derived the expected forms of PxAR and NxAR from a range of theoretical frameworks based on theory of island biogeography, neutral models, and species-area relationships. We constructed PxAR and NxAR in five empirical datasets on butterflies, plants, trees and birds, collected over range of spatial scales.\n\nResultsBoth the theoretical arguments and empirical data support monotonically decreasing PxAR, i.e. per-species extinction probability decreasing with increasing area; however, we also report a rare theoretical possibility of locally increasing PxAR. In contrast, both theory and data revealed complex NxAR, i.e. counts of extinction events follow variety of relationships with area, including nonlinear unimodal, multimodal and U-shaped relationships, depending on region and taxon.\n\nMain conclusionsThe uncovered wealth of forms of NxAR can explain why biodiversity change (the net outcome of losses and gains) also appears scale-dependent. Furthermore, the complex scale dependence of PxAR and NxAR means that global extinctions indicate little about local extirpations, and vice versa. Hence, effort should be made to understand and report extinction crisis as a scale-dependent problem. In this effort, estimation of scaling relationships such as PxAR and NxAR should be central.

ecology↗