The evolutionary age-range size relationship is modulated by insularity and dispersal in plants and animals

Abstract

Earth is home to millions of plant and animal species, with more than 40 thousand species facing extinction worldwide (Diaz et al. 2019). Species’ range size is particularly important in this context because it influences extinction risk (Purvis et al. 2000, Gaston & Fuller 2009), but the causes underlying the wide natural variation in range size remain poorly known. Here, we investigate how evolutionary age is related to present-day range size for over 25,000 species of mammals, birds, reptiles, amphibians, reef fishes, and plants. We show that, on average, older species have significantly larger ranges, but the effect of age on range size is modulated by clade, geographical context and dispersal ability. Specifically, age does not affect range size for island species, because islands limit dispersal and hence range size, regardless of species age. Furthermore, species from clades with high dispersal capabilities obtain large ranges faster, thereby further neutralizing the relationship between age and range size. Our results can help supporting global conservation priorities, by showing that species that are young, occupy islands, and/or are dispersal limited often have small ranges and therefore increased extinction risk.

Challenges in estimating species age from phylogenetic trees

“…The lowest error in species age estimation was observed under scenarios of bifurcating speciation. This is the implicit assumption of most studies using approximations of species ages (Alzate et al, 2023; Freer et al, 2022; Kennedy et al, 2022), even though it is at odds with the assumption of all birth-death models used in the molecular clock analyses that estimate the phylogenetic trees in the first place (Gernhard, 2008; Nee et al, 1994; Stadler, 2013). Despite the lower error, our simulations showed that both extinction and missing lineages can lead to a substantial decrease in accuracy (Fig.…”

“…More recently, several studies have used the length of terminal branches in time-calibrated phylogenies as a proxy for the age of extant species, an approximation that we hereafter refer to as "phylogenetic age" (Alzate et al, 2023;Davies et al, 2011;Gaston & Blackburn, 1997;Johnson et al, 2002;Pie & Caron, 2023;Sonne et al, 2022;Tanentzap et al, 2020;Verde Arregoitia et al, 2013). These phylogenetic ages have been used as the basis to test for links between species age and current extinction risks (Tanentzap et al, 2020;Verde Arregoitia et al, 2013) and to assess various correlations with evolutionary, biogeographical, and ecological patterns in living species (Alzate et al, 2023;Freer et al, 2022;Kennedy et al, 2022;Pie & Caron, 2023) While several studies have used phylogenetic age at face value for species age (e.g., Johnson et al 2002;Tanentzap et al 2020;Verde Arregoitia et al 2013), their potential deviation from the true species ages remains unclear. Specifically, we identify three nonmutually exclusive shortfalls that can lead to over-or underestimation of species ages.…”

“…Species ages estimated from paleobiological data offer a reliable measure of species’ temporal duration which can be used in macroevolutionary studies (Benton, 2016; Silvestro et al, 2020; Van Valen, 1973). More recently, several studies have used the length of terminal branches in time-calibrated phylogenies as a proxy for the age of extant species, an approximation that we hereafter refer to as “phylogenetic age” (Alzate et al, 2023; Davies et al, 2011; Gaston & Blackburn, 1997; Johnson et al, 2002; Pie & Caron, 2023; Sonne et al, 2022; Tanentzap et al, 2020; Verde Arregoitia et al, 2013). These phylogenetic ages have been used as the basis to test for links between species age and current extinction risks (Tanentzap et al, 2020; Verde Arregoitia et al, 2013) and to assess various correlations with evolutionary, biogeographical, and ecological patterns in living species (Alzate et al, 2023; Freer et al, 2022; Kennedy et al, 2022; Pie & Caron, 2023)…”

The relationships between species age and range size

“…climate) may change in the future (Farnsworth et al, 2023;Taylor, 2004) and whether it can adequately adapt. With the rapid development in phylogenetic studies (Alzate et al, 2023;Ramirez-Barahona et al, 2020), absolute age data are easier to be estimated (although extinct species are missing from the analysis) and we could examine how their current range sizes might be related to their absolute ages (times since species formation), which is also important for understanding many macroecological and biogeographical patterns and processes (Gaston & Blackburn, 1997). For example, all living species are a 'mixed bag' that includes species' ranges either expanding or contracting, but their relative fractions remain unknown.…”

“…Some recent studies also show that species richness is strongly associated with species range size (Guo et al, 2022; see also Shipley & McGuire, 2023). Recently, species' age has been increasingly cited as a possible major factor that may have contributed to determining species range size (Alzate et al, 2023;Guo et al, 2022;Webb & Gaston, 2000), but its contribution has rarely been examined with empirical data, especially for large species groups (e.g. vertebrate classes) and at a global scale (Gaston & Blackburn, 1997;Webb & Gaston, 2000).…”