Termites and savannas – an overview on history and recent scientific progress with particular respect to West Africa and to the genus Macrotermes

Abstract

Particularly in savannas, termites are ecosystem engineers and a keystone group in ecology. For the understanding of the savanna vegetation, mound building termites are of particular interest. Due to their special soil chemistry and physical structure, termite mounds often host other plants than the surrounding savanna. As our knowledge of the specific contribution of mound-building termites to overall savanna diversity and ecosystem dynamics doubtlessly is not complete, this paper summarises the state of the art in order to stimulate further research. According to the research interest of the authors, focus is laid on the West African savanna and on the genus Macrotermes.

Evolution at the arid extreme: the influence of climate on sand termite colonies and fairy circles of the Namib Desert

“…The bodies of Macrotermes termites, as well as termites in general, are extremely vulnerable to dehydration. The large colonies of Macrotermes are capable of providing for their water needs by 'mining' for soil water stored at great depth via their extensive tunnel systems [46][47][48][49] and bringing moisture-laden soil up to the large colony and its fungus garden. The cemented exterior of the tall mound impedes water losses through evaporation and also provides protection from predators [50].…”

Need for shared internal mound conditions by fungus-growing Macrotermes does not predict their species distributions, in current or future climates

“…Erpenbach & Wittig [29] and Bignell & Eggleton [30] give useful overviews of the key role of termites in African ecosystems. They are often key drivers of landscape heterogeneity and diversity through impacts on pattern and process [31].…”

“…Fungusgrowing termite species are monophyletic, implying that fungus cultivation evolved only once. Reversal to nonfungus cultivation apparently has not occurred [28], royalsocietypublishing.org/journal/rstb Phil. Trans.…”

“…The variation allowed by cultivation of different strains of Termitomyces is limited to only a few degrees, however. Other species, like M. bellicosus in Ivory Coast, seem to have only a single strain of fungal symbiont [25,28]. This might help explain why its distribution is limited largely to the savannah, with lower mound densities in forest habitats [52].…”

Mammalian herbivore movement into drought refugia has cascading effects on savanna insect communities

“…In African savannas, the large epigeal mounds constructed by the termite genus Macrotermes are associated with increased quantities of organic and inorganic materials relative to the savanna matrix (Seymour et al, 2014;Turner, 2019) and are considered nutrient and moisture hotspots (Erpenbach et al, 2013;Erpenbach & Wittig, 2016;Gosling et al, 2012). The increase in nutrients and water availability on mounds results in distinct floral communities Moe et al, 2009), that also have higher nutrient concentrations Grant & Scholes, 2006) and consequently are attractive to both insect and mammalian herbivores .…”