Good-bye to tropical alpine plant giants under warmer climates? Loss of range and genetic diversity in Lobelia rhynchopetalum.

Desalegn Chala,Achilleas Psomas,Niklaus E Zimmermann,Christian Brochmann,Catherine A Masao,Vegar Bakkestuen,Dorothee Ehrich,Abel Gizaw

doi:10.1002/ece3.2603

Abstract

The main aim of this paper is to address consequences of climate warming on loss of habitat and genetic diversity in the enigmatic tropical alpine giant rosette plants using the Ethiopian endemic Lobelia rhynchopetalum as a model. We modeled the habitat suitability of L. rhynchopetalum and assessed how its range is affected under two climate models and four emission scenarios. We used three statistical algorithms calibrated to represent two different complexity levels of the response. We analyzed genetic diversity using amplified fragment length polymorphisms and assessed the impact of the projected range loss. Under all model and scenario combinations and consistent across algorithms and complexity levels, this afro‐alpine flagship species faces massive range reduction. Only 3.4% of its habitat seems to remain suitable on average by 2,080, resulting in loss of 82% (CI 75%–87%) of its genetic diversity. The remaining suitable habitat is projected to be fragmented among and reduced to four mountain peaks, further deteriorating the probability of long‐term sustainability of viable populations. Because of the similar morphological and physiological traits developed through convergent evolution by tropical alpine giant rosette plants in response to diurnal freeze‐thaw cycles, they most likely respond to climate change in a similar way as our study species. We conclude that specialized high‐alpine giant rosette plants, such as L. rhynchopetalum, are likely to face very high risk of extinction following climate warming.

Highlights

Both climate change and land use intensification following population pressure (Grünenfelder, 2005; Hedberg, 1964) are potential threats to high-altitude species in tropical alpine habitats
Species that are confined to marginal areas such as mountain tops, polar regions, and islands may not have sufficient suitable habitat left to escape climate change and may face massive range contraction associated with high risks of extinction (Dullinger et al, 2012; Lenoir et al, 2008)
| 7 of the species would be further fragmented and confined to four mountaintops (Figure 3). Another 13.9% of the current range would present uncertain habitat suitability due to differences among climate and statistical models, complexity levels and thresholds (Table 1), which translated to a total of 82.6%–96.6% range loss for L. rhynchopetalum

Summary

| INTRODUCTION

Both climate change and land use intensification following population pressure (Grünenfelder, 2005; Hedberg, 1964) are potential threats to high-altitude species in tropical alpine habitats. Many giant rosette plants are only distantly related phylogenetically, they have developed similar distinctive morphological, physiological, and life history adaptations to the diurnal freeze-thaw cycles of tropical alpine habitats (Halloy, 1983). These complex adaptations include the following: (i) retaining old leaves as a shelter, (ii) accumulating water within body parts to minimize thermal shocks, and (iii) having large rosette leaves which fold during the freezing nights through nyctinastic leaf movements to protect the delicate buds. We estimate to what degree genetic diversity is geographically structured in these archipelago-like African high mountains and predict loss of genetic diversity due to climate-driven range loss

| MATERIALS AND METHODS

Findings

| DISCUSSION