Climatic niche shift in the amphitropical disjunct grass Trichloris crinita

Abstract

Plant species disjunctions have attracted the interest of ecologists for decades. We investigated Trichloris crinita, a native C4 perennial grass with disjunct distribution between subtropical regions of North and South America, testing the hypothesis that the species has a similar realized climatic niche in both subcontinents. The climatic niche of T. crinita in North and South America was characterized and compared using presence records and five uncorrelated bioclimatic variables selected according to their ecological importance for the species. We used reciprocal modeling to make geographic projections of the realized niche within each subcontinent. Niche overlap between T. crinita distributions in North and South America was intermediate for the individual climatic variables and the multivariate space. In all cases the test of equivalence between climates inhabited by T. crinita indicated that the realized niche of the species differ significantly between subcontinents. Also, the similarity test showed that in the majority of cases the realized niche in both subcontinents was significantly different than that expected by chance. T. crinita occupied a greater diversity of environments in South than in North America, while in the latter its distribution was displaced to drier and warmer environments. The modeled geographic distribution using the actual occurrences of the species in North America did not accurately predict the distribution in South America, and vice versa. Together, these results led us to reject the hypothesis of similar niche of T. crinita in both subcontinents. This information may be useful to manage restoration efforts by presenting the suitable areas and climates for the species, and suggesting that translocation of individuals between subcontinents could only be recommended with caution because introduced genotypes can be potentially maladaptive, and could colonize sites actually not occupied by the species within each subcontinent.

Niche dynamics in amphitropical desert disjunct plants: Seeking for ecological and species‐specific influences

“…The only species in which we did not find any signal of niche shift was the grass Lycurus setosus (Table 1). Our main results match a previous finding for the amphitropical disjunct grass Trichloris crinita (not included in this study), which showed a significant niche shift between North and South America, both in the statistical and the biological sense (R. E. Quiroga et al., 2018). As for that species, we here show that most of the amphitropical desert disjunct species in South America have their niches in cooler environments than in North America (25‐species AMT average = −2.5 °C [5 and 95% confidence limits −1.3 and −3.7 °C], p = .0003, paired t test, n = 25; see also Figure 2 and Figures S1.4–6 in Supporting Information Appendix S1).…”

“…Our work and accumulating evidence from other studies (Atwater et al., 2018; R. E. Quiroga et al., 2018; J. R. Shipley et al., 2013; Villaverde et al., 2017; Wasof et al., 2013) show that it is not advisable to assume a priori that the niche of a species would be conserved from a region to another (i.e. to predict areas of invasion) or from one moment to another (i.e.…”

“…Of the entire set, five variables were selected due to their biological importance for the studied species (Early & Sax, 2014; Guisan et al., 2014) and retained for further analyses; they were not highly correlated with each other ( r < .85; Wei et al, 2017; Pearson’s correlation analysis performed with ENMTools v1.4.4; Warren et al., 2010). The five variables we selected are related to the availability of water and temperature during the summer growing season and the entire year, as well as to the annual range of temperatures that the species endure (Cabido et al., 1997; R. E. Quiroga et al., 2018; Raven, 1963). They were: precipitation of the warmest quarter (PWQ), annual precipitation (AP), mean temperature of the warmest quarter (MTWQ), annual mean temperature (AMT) and temperature annual range (TAR, difference between the mean maximum temperature of warmest month and the mean minimum temperature of the coldest month).…”

“…However, conservatism was also the general pattern found in a study of 31 native plants naturally disjunct between the European Alps and Scandinavia, with only one species showing niche shift between both regions (Wasof et al., 2015). Moreover, in a recent study we provided evidence of realized niche differentiation for the disjunct perennial grass Trichloris crinita that inhabits North and South America, that is, not invasive in either continent (R. E. Quiroga et al., 2018). Thus, the use of species that have naturally inhabited different regions for a long time (i.e.…”

Refugia during the last glacial period and the origin of the disjunct distribution of an insular plant

“…In addition, we built and evaluated separate distribution models using the occurrence data for the HI region (39 records) or the KRT region (91 records) (Table S4). This kind of modelling technique is called reciprocal ENM (Fitzpatrick et al, 2007; Peterson et al, 1999), and has often been applied to estimate niche shifts of congeneric species with disjunct distributions (Liu et al, 2017; Quiroga et al, 2018).…”