ECR feature: Maria Guerrina on post-glacial contraction in an Alpine endemic plant.

Maria Guerrina is a postdoc at the Università degli Studi di Genova in Italy. She is a plant biologist interested in the evolution of endemic biota. Here, Maria shares her recent work on the post-glacial contraction of an Alpine endemic species.

Maria Guerrina during fieldwork in the South-western European Alps.

Personal links. Research Gate

Institute. Dipartimento di Scienze della terra, dell’ambiente e della vita (DISTAV) – Università degli Studi di Genova.

Academic life stage. Postdoc

Major research themes. Endemic species, conservation, glacial refugia, climate change, reproductive biology, alpine flora, phylogeography.

Current study system. My study species is Berardia subacaulis Vill., the only living species belonging to a monospecific genus endemic to the South-western European Alps. This cold-adapted species is a relic of the Tertiary paleo flora (~24 mya), which almost went completely extinct during Late Quaternary climatic oscillations. Being such an “ancient” species makes it interesting and necessary to understand how past climatic changes affected the demographic history of this species. By doing so, we can make more reliable predictions on how it will respond to future pressures.

Maria out in the field collecting leaves of B. subacaulis.

Recent JBI paper. Guerrina M, Theodoridis S, Minuto L, Conti E,Casazza G (2022) First evidence of post-glacial contraction of Alpine endemics: insights from Berardia subacaulis in the European Alps. Journal of Biogeography. 49 (1): 79-93

Motivation behind this paper. This study sought to understand the possible responses of plants to the Late Quaternary dynamics (i: post-glacial expansion; ii: post-glacial contraction; and iii: long-term stability). The study is located in the South-western European Alps (SW Alps). This area was less affected by the glaciations than the rest of the Alps because of the Mediterranean Sea influence. Given the proximity of the SW Alps to the Mediterranean and Alpine climates, the region is characterized by high local climatic variability and topographic heterogeneity, which promoted a variety of phylogeographical patterns in the biota. Until today, two common hypotheses have been proposed: post-glacial expansion or long-term stability (mainly by altitudinal shift). However, an interesting pattern never yet detected is the expansion of cold-adapted species during glaciation due to the limited extent of the glacial sheet in the area, followed by a population contraction after glaciation.

A blooming individual of B. subacaulis. It is possible to see the secondary presentation of pollen on the stigma in the central open flowers.

Key methodologies. Our paper relies on species distribution models (SDMs) throughout the last 28 Ky and genome-wide sequences (genotyping-by-sequencing; GBS) to estimate current spatial structure patterns from genetic diversity. Because B. subacaulis grows only on specific calcareous substrates, we added substrate information into the in SDMs to report the presence/absence of this suitable substrate, based on the global lithological map dataset (GLiM). Integrating the results of the two independent approaches (SDMs and GBS) allowed us to test several demographic models under an Approximate Bayesian Computation framework.

Unexpected challenges. One of the biggest challenges we faced was field sampling. Berardia subacaulis grows on very steep scree, and this kind of habitat did not make sampling easy! Because of it, before starting the sampling, I went shopping for comfortable boots for walking on scree – the clerk looked at me strangely! The sampling season began with two outings of about eight hours of hiking each before we managed to find the plant (I’m glad I got proper boots!). Funny thing, I was with a colleague, and none of us had ever seen the plant before. But it was really nice to find some populations following herbarium information from the end of the 19th century.

Achenes of B. subacaulis.

Major results. For the first time, we provide empirical evidence of post-glacial demographic contraction and a recent split between the two genetic groups for an endemic plant in the European Alps during the Late Quaternary. The pattern observed might be due to several factors. First, the SW Alps were characterized by greater availability of ice-free terrain during the Last Glacial Maximum (LGM) because of the Mediterranean Sea mitigation that maintained temperatures some degrees higher than in the rest of the Alps. Second, the SW Alps were characterized by relatively high precipitation, which, combined with the ice-free areas, might have allowed B. subacaulis to persist or even expand in most climatically suitable areas at high altitudes during the LGM.

Next steps for this research. Several hypotheses explaining patterns of endemism have been explicitly tested at the global scale, raising questions about the persistence of biodiversity during the present era of changing climate. However, these hypotheses have never been tested at local scales, and the SW Alps are an interesting place to test them. The next step in this research is to explore the environmental drivers promoting endemic richness distribution in the SW Alps.

Typical habitat of B. subacaulis, growing on steep calcareous scree.

If you could study any organism on Earth, what would it be? Plants, I cannot change my study organism! In particular, I would like to study any rare and endemic plants with peculiarities, such as blooming every 40 years or growing in almost inaccessible places.

Published by jbiogeography

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