Late Cenozoic climate and the phylogenetic structure of regional conifer floras world‐wide

Abstract

Aim Using conifers as a model system, we aim to test four hypotheses. H1: the processes that shape the phylogenetic structure of regional species assemblages depend on climate. H2: apparent effects of current climate can be equally well explained by past climate. H3: strong Quaternary climate oscillations have led to phylogenetically non‐random assemblages, either with few closely related species because isolated populations do not persist long enough to become new species or with many close relatives due to increased allopatric speciation. H4: strong late Cenozoic aridification has led to assemblages with many close relatives due to extinction and adaptive radiation. Location Global. Methods We used boosted regression trees to relate the net relatedness index (NRI) of regional conifer assemblages to current climate, past climate (0.021, 3 and 7.3–11.6 Ma), and gradual and cyclic late Cenozoic climate change while simultaneously accounting for habitat and biogeographic covariates. Results Climate was the most important predictor of NRI, supporting H1. Current and past climate showed similar relationships with NRI, supporting H2. Conifer NRI was further related to Quaternary climate oscillations and gradual late Cenozoic climate trends, but the shape of the relationships supported neither H3 nor H4. Main conclusions The climate–NRI relationships suggest that late Cenozoic climate consistently influenced the dynamics of conifer speciation, extinction and dispersal, leading to global patterns of phylogenetic assemblage structure. We deduce from the phylogenetic structure that diversification has been highest in warm or dry climates over the last ≥11.6 Myr. The fact that phylogenetic structure is related to climate trends and oscillations indicates that climate change plays an important role in addition to climate per se, but the exact underlying mechanisms remain unclear. Our results suggest that past climate needs to be taken into account when aiming to explain the phylogenetic structure of regional assemblages and other related aspects of biodiversity.

Phylogenetic assemblage structure of North American trees is more strongly shaped by glacial–interglacial climate variability in gymnosperms than in angiosperms

“…Although this could suggest that there is only weak‐to‐moderate disequilibrium in North American angiosperm's response to climate, these current climate associations may be confounded with past climate effects on the biogeography of phylogenetic assemblage structures due to correlations between past and present geographic climate configurations (Eiserhardt et al. ). The fact that phylogenetic clustering of angiosperms decreased almost monotonically with temperature (Fig.…”

“…We note that relations to current climate may in fact reflect relations to correlated deeper‐time climate patterns (Eiserhardt et al. ). Higher phylogenetic diversity and endemism occurs in areas less affected by glacial–interglacial climate instability and glaciation, that is, in areas with more stable climate (Sandel et al. ) or more heterogeneous topography, as this buffers against climate change (Ackerly et al.…”

“…As a result, the biodiversity patterns observed at the current time may be also influenced by climate conditions in the past (Eiserhardt et al. ). Thus, in the fast‐changing climate of the Anthropocene, biodiversity pattern studies, conservation management, and planning should rely on more explicit determination of the time lags involved in the biodiversity–climate relationships (Dullinger et al.…”

Environmental correlates of phylogenetic endemism in amphibians and the conservation of refugia in the Coastal Forests of Eastern Africa

“…For historical stability, we used two measures of Quaternary climate change, measured as the absolute difference in mean annual temperature and precipitation between the Last Glacial Maximum (LGM) and the present (see Kissling et al, 2012). These measures serve as proxies to represent the effect of climatic oscillations during the Quaternary (Eiserhardt, Borchsenius, Sandel, Kissling, & Svenning, 2015;Sandel et al, 2011). We also prepared a measure of historical forest stability over time following Graham, VanDerWal, Phillips, Moritz, and Williams (2010).…”

Steep topography buffers threatened gymnosperm species against anthropogenic pressures in China

“…Globally, gymnosperms represent one of the most vulnerable groups of living species with almost 40% of all species threatened according to the International Union for Conservation of Nature (IUCN) Red List (Brummitt et al, ; Fragnière, Bétrisey, Cardinaux, Stoffel, & Kozlowski, ), and China is host to more than 10% of the most threatened evolutionary distinct species (so‐called EDGE species) of this group (Forest et al, ). China thus constitutes a global hotspot for gymnosperm diversity, with ~250 species and many threatened, relict lineages such as Ginkgo biloba , Cathaya argyrophylla , and Taiwania cryptomerioides (Eiserhardt, Borchsenius, Sandel, Borchsenius, Sandel, Kissling, & Svenning, ; López‐Pujol et al, ; Qian, ).…”