Biology subjects

Graco-Roza, C.

Publications and source records attributed to Graco-Roza, C..

5 recordsLinked to original sources

bioRxiv2025

Macroinvertebrate diversity patterns in a guano-rich temperate cave

Most caves in temperate regions are energy-poor, leading to low richness and abundances of terrestrial macroinvertebrates. However, caves with abundant bat populations may represent a notable exception, as bat guano serves as a significant source of organic matter, supporting diverse specialized invertebrates. Yet, given the overall rarity of guano-rich caves in temperate region, their ecological dynamics are poorly understood. We conducted a year-long monthly standardized monitoring of the macroinvertebrates of the Buca dei Ladri cave, a guano-rich cavity in Tuscany, Italy. At each survey, we counted species within different sampling quadrats and collected environmental variables such as temperature, structural heterogeneity of the substrate, dominant substrate, and presence of bats. Over the year, we identified 31 macroinvertebrate species in the cave as both morphospecies and molecular lineages, based on mitochondrial COI and nuclear 18S genes. The latter approach hinted at the presence of cryptic diversity in some species. We observed an increase in species diversity with increasing structural complexity and the presence of bats, whereas a lower species diversity was found in guano-dominated substrates, probably due to the old age and subsequent low nutritional value of the historical guano deposits. Changes in the abundance of species within the cave were primarily explained by differences in structural complexity across sampling quadrats, whereas the distance from the cave entrance mostly explained species replacement. Our results underscore the importance of preserving healthy bat populations and a high habitat heterogeneity within the cave for the long-term conservation of the unique macroinvertebrate assemblages of the cave.

ecology↗

bioRxiv2023

Functional convergence underground? The scale-dependency of community assembly processes in European cave spiders

Understanding how species assemble into communities is a central tenet in ecology. One of the most elusive questions is the relative contribution of environmental filtering versus limiting similarity. Important advances in this area have been achieved by looking at communities through a functional lens (i.e., the traits they express), so as to derive principles valid across species pools. Yet, even using traits in lieu of taxonomy, the issue remains controversial because i) environmental filtering and limiting similarity often act simultaneously in shaping communities; and ii) their effect is scale-dependent. We exploited the experimental arena offered by caves, island-like natural laboratories characterized by largely constant environmental gradients and a limited diversity of species and interactions. Leveraging uniquely available data on distribution and traits for European cave spiders, we tested explicit hypotheses about variations in community assembly rules across ecological gradients and scales. We demonstrate that environmental filtering and limiting similarity shape cave communities acting on trait evolution in opposing directions. These effects are strongly scale dependent, varying along multiple environmental gradients. Conversely, the effect of geography on trait composition is weak, indicating that trait turnover in space happens primarily by substitution of species pursuing similar functions due to strong environmental filters. Our findings reconcile contrasted views about the relative importance of the two main mechanisms shaping patterns of biodiversity, and provide a conceptual foundation to account for scaling effects in the study of community assembly.

ecology↗

bioRxiv2022

Calculating functional diversity metrics using neighbor-joining trees

O_LIThe study of functional diversity (FD) provides ways to understand phenomena as complex as community assembly or the dynamics of biodiversity change under multiple pressures. Different frameworks are used to quantify FD, either based on dissimilarity matrices (e.g., Rao entropy, functional dendrograms) or multidimensional spaces (e.g. convex hulls, kernel-density hypervolumes). While the first does not enable the measurement of FD within a richness/divergence/regularity framework, or results in the distortion of the functional space, the latter does not allow for comparisons with phylogenetic diversity (PD) measures and can be extremely sensitive to outliers. C_LIO_LIWe propose the use of neighbor-joining trees (NJ) to represent and quantify functional diversity in a way that combines the strengths of current FD frameworks without many of their weaknesses. Our proposal is also uniquely suited for studies that compare FD with PD, as both share the use of trees (NJ or others) and the same mathematical principles. C_LIO_LIWe test the ability of this novel framework to represent the initial functional distances between species with minimal functional space distortion and sensitivity to outliers. The results using NJ are compared with conventional functional dendrograms, convex hulls, and kernel-density hypervolumes using both simulated and empirical datasets. C_LIO_LIUsing NJ we demonstrate that it is possible to combine much of the flexibility provided by multidimensional spaces with the simplicity of tree-based representations. Moreover, the method is directly comparable with PD measures, and enables quantification of the richness, divergence and regularity of the functional space. C_LI

ecology↗

bioRxiv2021

Distance decay 2.0 - a global synthesis of taxonomic and functional turnover in ecological communities.

Understanding the variation in community composition and species abundances, i.e., {beta}-diversity, is at the heart of community ecology. A common approach to examine {beta}-diversity is to evaluate directional turnover in community composition by measuring the decay in the similarity among pairs of communities along spatial or environmental distances. We provide the first global synthesis of taxonomic and functional distance decay along spatial and environmental distance by analysing 149 datasets comprising different types of organisms and environments. We modelled an exponential distance decay for each dataset using generalized linear models and extracted r2 and slope to analyse the strength and the rate of the decay. We studied whether taxonomic or functional similarity has stronger decay across the spatial and environmental distances. We also unveiled the factors driving the rate of decay across the datasets, including latitude, spatial extent, realm, and organismal features. Taxonomic distance decay was stronger along spatial and environmental distances compared with functional distance decay. The rate of taxonomic spatial distance decay was the fastest in the datasets from mid-latitudes while the rate of functional decay increased with latitude. Overall, datasets covering larger spatial extents showed a lower rate of decay along spatial distances but a higher rate of decay along environmental distances. Marine ecosystems had the slowest rate of decay. This synthesis is an important step towards a more holistic understanding of patterns and drivers of taxonomic and functional {beta}-diversity.

ecology↗

bioRxiv2019

Clumpy coexistence in phytoplankton: The role of functional similarity in community assembly

AO_SCPLOWBSTRACTC_SCPLOWEmergent neutrality (EN) suggests that species must be sufficiently similar or sufficiently different in their niches to avoid interspecific competition. Such a scenario results in a transient pattern with clumps and gaps of species abundance along the niche axis (e.g., represented by body size). From this perspective, clumps are groups of coexisting species with negligible fitness differences and stochastic abundance fluctuations. Plankton is an excellent model system for developing and testing ecological theories, especially those related to size structure and species coexistence. We tested EN predictions using the phytoplankton community along the course of a tropical river considering (i) body size structure, (ii) functional clustering of species in terms of morphology-based functional groups (MBFG), and (iii) the functional similarity among species concerning their functional traits. Two main clumps in the body size axis (clump I and II) were conspicuous through time and were detected in different stretches of the river. Clump I comprised medium-sized species from the MBFGs IV, V, and VI while clump II included large-bodied species from the MBFGs V and VI. Pairwise differences in species biovolume correlated with species functional similarity when the whole species pool was considered, but not among species within the same clump. Although clumps comprised multiple MBFGs, the dominant species within the clump belonged always to the same MBFG. Also, within-clump species biovolume increased with functional distinctiveness considering both seasons and stretches, except the lower course. These results suggest that species within clumps behave in a quasi-neutral state, but even minor shifts in trait composition may affect species biovolume. Our findings point that EN belongs to the plausible mechanisms explaining community assembly in river ecosystems.

ecology↗