Fern species richness and abundance are indicators of climate change on high-elevation islands: evidence from an elevational gradient on Tahiti (French Polynesia)

Abstract

Inherent characteristics of island species make them particularly susceptible to anthropogenic changes and need to be assessed to implement appropriate conservation strategies. The impacts of climate change are increasingly being investigated along elevational gradients since they provide natural laboratories to study how species respond to climatic variation. Ferns are particularly sensitive to air humidity and temperature and are therefore potentially useful as bio-indicators. This study addresses the question of whether the distributions of fern species richness and abundance have climatic correlates along an elevational gradient on the tropical volcanic island of Tahiti (French Polynesia). Analyses were conducted on two datasets: island-wide richness was estimated using published data on species elevational ranges, and local richness and abundance were addressed through a transect survey. Correlations with water availability, temperature, area availability, and a randomly-generated species richness pattern were investigated. Results showed that both diversity and abundance varied in association with climate. Rainfall was collinear with diversity in the lower half of the elevational gradient (R 2 = 0.97), while temperature was the most important climatic correlate Climatic Change for diversity in the upper half (R 2 = 0.98). The number of terrestrial fern individuals and epiphytic fern cover were both correlated with temperature (R 2 = 0.86 and 0.81, respectively). Our results imply that impacts of climate change on ferns on Tahiti might include change in diversity and abundance, and increased extinction risk due to low overlap between current and projected species distributions. Ferns represent important indicator organisms that can be used to study species distributional responses to climate change in island ecosystems.

Community assembly of the ferns of Florida

“…() found that the level of phylogenetic clustering differed between the life stages and with elevation, with sporophytes showing evidence of phylogenetic clustering that grew stronger with increasing elevation, while gametophytes showed no evidence of phylogenetic clustering at any elevation. These authors also found, strikingly, that gametophytes showed no evidence of the mid‐elevation peak in species richness that is a hallmark of fern species distributions across elevational gradients in the tropics, based entirely on studies of sporophytes (Cardelus et al., ; Kluge and Kessler, ; Watkins et al., ; Kluge et al., ; Kessler et al., ; Pouteau et al., ). These findings together strongly suggest that gametophytes are governed by different assembly rules than are sporophytes.…”

Life cycle matters: DNA barcoding reveals contrasting community structure between fern sporophytes and gametophytes

“…It is possible that including the gametophyte phase may also reveal different patterns from those observed in sporophytes in other transect studies. Pouteau et al (2016) analyzed the same sporophyte plot data as well as island-wide diversity of fern sporophytes on Tahiti, and found that climate seems to explain the observed richness peak better than the mid-domain effect (i.e., species richness peak due to randomly distributed elevational ranges within a bounded space; Colwell and Lees 2000).…”

Taxonomic, Phylogenetic, and Functional Diversity of Ferns at Three Differently Disturbed Sites in Longnan County, China

“…Ferns are distributed globally, but they have the highest density in the tropical mountains [4]. Ferns are sensitive to the indicators of environmental conditions [5][6][7][8][9][10], with various adaptative strategies to variations in climatic and edaphic parameters [11,12]. Hence, fern diversity shows clear patterns along environmental gradients at different spatial scales [8,13,14].…”

“…In contrast to many other groups of plants and animals, the taxonomic diversity of fern gradients generally follows a hump-shaped unimodal pattern along the elevational gradient [4,9,10,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. The main drivers for such unimodal patterns are the combined effects of different climatic factors, including the temperature, precipitation, and cloud cover [4,[8][9][10]21,[27][28][29][30][31][32][33][34][35]. Generally, fern diversity tends to be high in temperate and humid habitats but low in cold, hot, and arid habitats [10,36].…”