The Ecophysiology of the Enigmatic Namib Succulent, Lithops ruschiorum

Author

Garrett MacLeod AlthausenFollow

Date of Award

Spring 6-2-2025

Document Type

Thesis (Undergraduate)

Department

Environmental Studies

First Advisor

Douglas Bolger

Abstract

Water availability is the primary constraint for plant survival and reproduction in hyper-arid ecosystems. In such environments, plant fitness depends on an alignment between physiological traits and limited water resources. The Namib Desert of Namibia exemplifies this extreme selection pressure. Within the Namib Desert, Lithops ruschiorum, a succulent endemic to the gravel plains, exhibits habitat specificity and numerous physiological adaptations to cope with the hyper-aridity.

This research explores the intersection of two fitness strategies for L. ruschiorum: habitat selection and exploitation of alternative moisture sources. The first chapter explores the population dynamics and micro-site habitat conditions preferred by L. ruschiorum. Our population surveys between 2007 and 2024 revealed a significant decline in abundance of L. ruschiorum, with several populations approaching local extinction. The habitat distribution analysis indicated that topographic position and substrate type best predict habitat occupancy for L ruschiorum possibly due to the potential for fog capture and retention. Our second chapter investigates the hypothesis that fog, as opposed to rain or groundwater, serves as the primary water source used by L. ruschiorum. Stable isotope analyses, foliar capacity tests and fluorescent microscopy indicated that L. ruschiorum supplements its water budget through the foliar uptake of fog. These findings suggest that the species’ survival depends on highly specific microhabitats and fog water inputs. With the growing threats of climate change and poaching, L. ruschiorum is vulnerable to irreparable population loss. An understanding of the environmental factors determining the species’ distribution and its primary water source inform conservation and restoration strategies for the long-term survival of the species.

Recommended Citation

Althausen, Garrett MacLeod, "The Ecophysiology of the Enigmatic Namib Succulent, Lithops ruschiorum" (2025). Environmental Studies Senior Theses. 12.
https://digitalcommons.dartmouth.edu/environmental_studies_senior_theses/12