Investigating elevational gradients of species richness in a Mediterranean plant hotspot using a published flora

Abstract

Highlights• The published flora of the Apuan Alps was explored to detect biogeographical patterns.• Native and alien plant species richness decreased with elevation, while endemics increased, pointing at the conservation relevance of the Apuan Alps.• Functional groups based on Raunkiaer Life Forms show differentiated responses to the elevational gradient.• Area size of elevational belts have only marginal effects on patterns of species richness: the observed trends are likely due to environmental constraints.• Current climate change is likely to affect observed patterns, high-elevation rare species are likely to be threatened by competition from species moving upwards from lower elevations.

Mountain biodiversity and elevational gradients

“…The flowering plant diversity papers report from studies in the Apuan Alps (Italy) (Musciano et al 2021) and the Himalayas (Bhatta et al 2021), the former from the warm temperate Mediterranean climate and the latter from subtropical monsoon climate. These two papers use an established approach of interpolated species richness from upper and lower range limits compiled from flora and/ or enumerations.…”

Variations in Plant Richness, Biogeographical Composition, and Life Forms along an Elevational Gradient in a Mediterranean Mountain

“…Since species responses to environmental factors are mediated by their traits and are reflected by their distribution, vegetation studies frequently take advantage by classifying species into life forms [23][24][25][26][27] and biogeographical categories [28][29][30][31][32]. Surprisingly enough, however, only a few studies have investigated variations in plant biogeographical [18,33] and life form (e.g., [18,20,[33][34][35][36][37][38][39][40][41][42]) composition along elevational gradients.…”

“…Mountains in the Mediterranean environment are therefore excellent natural laboratories to investigate how chorotype and life form composition of plant assemblages change along the elevational gradient. However, very few research studies have investigated variation in chorological [33] and life form [20,33,41] composition along elevational gradient in Mediterranean mountains. Moreover, various sources of complexity influenced these studies, making comparisons and interpretations difficult.…”

“…Moreover, various sources of complexity influenced these studies, making comparisons and interpretations difficult. For example, both Lazarina et al [20] and Di Musciano et al [41] used elevational gradients extended over wide areas. When data are aggregated from sites dispersed over a wide area, the resulting elevational gradient may represent a heterogeneous combination of species assemblages belonging to floras influenced by different biogeographical and evolutionary processes operating on large scales.…”

“…To avoid these problems, it is important to focus on elevational gradients in geographically narrow areas. However, even in narrow scale approaches, a common procedure is that of using elevational bands and assuming that species are continuously distributed along the gradient, from the lowest to the highest belt [33,41]. This could lead to consider coexisting species that, although recorded at the same elevation, occupy different areas and do not form true communities.…”