The importance of common and the irrelevance of rare species for partition the variation of community matrix: implications for sampling and conservation

Abstract

In community ecology, it is important to understand the distribution of communities along environmental and spatial gradients. However, it is common for the residuals of models investigating those relationships to be very high (> 50%). It is believed that species’ intrinsic characteristics such as rarity can contribute to large residuals. The objective of this study is to test the relationship among communities and environmental and spatial predictors by evaluating the relative contribution of common and rare species to the explanatory power of models. Our hypothesis is that the residual of partition the variation of community matrix (varpart) models will decrease as rare species get removed. We used several environmental variables and spatial filters as varpart model predictors of fish and Zygoptera (Insecta: Odonata) communities in 109 and 141 Amazonian streams, respectively. We built a repetition structure, in which we gradually removed common and rare species independently. After the repetitions and removal of species, our hypothesis was not corroborated. In all scenarios, removing up to 50% of rare species did not reduce model residuals. Common species are important and rare species are irrelevant for understanding the relationships among communities and environmental and spatial gradients using varpart. Therefore, our findings suggest that studies using varpart with single sampling events that do not detect rare species can efficiently assess general distributional patterns of communities along environmental and spatial gradients. However, when the objectives concern conservation of biodiversity and functional diversity, rare species must be carefully assessed by other complementary methods, since they are not well represented in varpart models.

Seasonal Variations in the Biodiversity, Ecological Strategy, and Specialization of Diatoms and Copepods in a Coastal System With Phaeocystis Blooms: The Key Role of Trait Trade-Offs

“…Moreover, copepods live much longer than diatom cells (several months/up to 1 year for copepods, but a few days for diatoms) and their traits enable them to survive in unfavorable conditions. Large unexplained variance (>50%), as we quantified in the VP analysis, is common in ecological studies (Brasil et al, 2020 and references therein) and is often the result of (i) unmeasured environmental drivers, such as trace metals (Chappell et al, 2019); and (ii) potential antagonistic responses among species within a community (Brasil et al, 2020). Brasil et al (2020) have also recently provided evidence that the assessment of biodiversity and FD is influenced by the presence/lack of rare species: rarity can contribute to large residuals when varpart models are computed.…”

“…Large unexplained variance (>50%), as we quantified in the VP analysis, is common in ecological studies (Brasil et al, 2020 and references therein) and is often the result of (i) unmeasured environmental drivers, such as trace metals (Chappell et al, 2019); and (ii) potential antagonistic responses among species within a community (Brasil et al, 2020). Brasil et al (2020) have also recently provided evidence that the assessment of biodiversity and FD is influenced by the presence/lack of rare species: rarity can contribute to large residuals when varpart models are computed. The uncertainty in plankton counts [estimated to be 10% for diatoms based on the table of Lund et al (1958), and 3-40% for zooplankton (Mack et al, 2012;Kwong and Pakhomov, 2021) with an average of 30% (Frontier, 1969)] could have contributed to the large unexplained discrepancies found in the VP analyses (Brasil et al, 2020).…”

“…Brasil et al (2020) have also recently provided evidence that the assessment of biodiversity and FD is influenced by the presence/lack of rare species: rarity can contribute to large residuals when varpart models are computed. The uncertainty in plankton counts [estimated to be 10% for diatoms based on the table of Lund et al (1958), and 3-40% for zooplankton (Mack et al, 2012;Kwong and Pakhomov, 2021) with an average of 30% (Frontier, 1969)] could have contributed to the large unexplained discrepancies found in the VP analyses (Brasil et al, 2020). Uncertainty in the species carbon conversion factors that we used for the calculation may have also influenced the estimations and the initial assumptions on how to capture the biological responses, such as linearity of the relationships between the response and explanatory matrices or statistical normality.…”

Influence of human land use and invasive species on beta diversity of tropical ant assemblages

“…Consistent with theoretical expectations (Gaston et al ., 2006), we find a non‐monotonic curvilinear relationship with commonness and rarity (Fig. S6), such that the commonest as well as rare species may not have a strong influence on beta diversity (Brasil et al ., 2020). Previous studies have interpreted such covariation as monotonic and linear (Gavioli et al ., 2019), even though data are expected to be curvilinear and non‐monotonic.…”

“…So, it is likely that we recorded the common species adequately but may have missed few rare ones. This may not hinder broad inference from the data since common species play a greater role in beta diversity than the exceedingly rare ones (Brasil et al ., 2020).…”