DOI: 10.5061/dryad.2ngf1vhq0
title: You eat what you find – local patterns in vegetation structure control diets of African fungus-growing termites

description: Fungus-growing termites and their symbiotic Termitomyces fungi are
 critically important carbon and nutrient recyclers in arid and semiarid
 environments of sub-Saharan Africa. A major proportion of plant litter
 produced in these ecosystems is decomposed within nest chambers of termite
 mounds, where temperature and humidity are kept optimal for the fungal
 symbionts. While fungus-growing termites are generally believed to exploit
 a wide range of different plant substrates, the actual diets of most
 species remain elusive. We studied dietary niches of two Macrotermes
 species across the semiarid savanna landscape in the Tsavo Ecosystem,
 southern Kenya, based on carbon (C) and nitrogen (N) stable isotopes in
 Termitomyces fungus combs. We applied Bayesian mixing models to determine
 the proportion of grass and woody plant matter in the combs, these being
 the two major food sources available for Macrotermes species in the
 region. Our results showed that both termite species, and colonies
 cultivating different Termitomyces fungi, occupied broad and largely
 overlapping isotopic niches, indicating no dietary specialization.
 Including laser scanning derived vegetation cover estimates to the dietary
 mixing model revealed that the proportion of woody plant matter in fungus
 combs increased with increasing woody plant cover in the nest
 surroundings. Nitrogen content of fungus combs was positively correlated
 with woody plant cover around the mounds and negatively correlated with
 the proportion of grass matter in the comb. Considering the high N demand
 of large Macrotermes colonies, woody plant matter seems to thus represent
 a more profitable food source than grass. As grass is also utilized by
 grazing mammals, and the availability of grass matter typically fluctuates
 over the year, mixed woodland-grasslands and bushlands seem to represent
 more favorable habitats for large Macrotermes colonies than open
 grasslands.
description: Data originates from 59 termite mounds representing two
 <i>Macrotermes </i>species occurring in the Tsavo Ecosystem,
 Kenya. Each termite mound was georeferenced using a handheld GPS and the
 inhabitant termite species was identified based on species-specific mound
 morphology. The results of
 stable isotope (δ<sup>13</sup>C, δ<sup>15</sup>N)
 and elemental (C%, N%) analysis originate from a single fungus comb
 specimen collected from each studied mound. The analysis were performed at
 the Laboratory of Chronology, Finnish Museum of Natural History (Helsinki,
 Finland) using an NC2500 elemental analyzer coupled to a Thermo Scientific
 Delta V Plus isotope ratio mass spectrometer and the raw isotope data was
 normalized with a multi-point calibration using certified isotopic
 reference materials (USGS-40, USGS-41, IAEA-N1, IAEA-N2, IAEA-CH3 and
 IAEA-CH7). The species identity of the cultivated
 <em>Termitomyces </em>fungi (unnamed species "A",
 "B" or "C") is based on DNA barcoding of the ribosomal
 ITS1–5.8S–ITS2 region extracted from the fungal nodules growing on the
 comb surface (Vesala et al. 2017, 2019). Canopy cover was assessed around
 each termite mound using LiDAR (Light Detection and Ranging) point
 clouds produced during a flight campaign in March 2014. Lidar point clouds
 were classified and converted to topographic and surface models
 representing either ground or vegetation canopy, respectively, using
 Lastools processing software (https://rapidlasso.com/lastools/). A Canopy
 Height Model at 1 m spatial resolution was derived from topographic and
 surface models and was used to calculate precentage canopy cover using
 QGIS 3.6. Canopy cover around each studied mound was calculated separately
 for three different tree height classes (&gt; 1, 3 and 6 meters)
 within three different circular buffers (radiuses 35, 50 and 100 m)
 centered at mound centrum, leading to a total of nine different canopy
 cover estimates.
description: The principle data file
 <i>Fungus_comb_stable_isotopes_and_canopy_cover.csv </i>was
 used as the mixture dataset for the MixSIAR analysis. Additionally, the
 file includes the data needed to produce map illustration in Figure 2 and
 the regression models comparing fungus comb C:N stoichiometry and the
 canopy coverage or comb δ<sup>13</sup>C. Units of the stable
 isotope values (δ<sup>13</sup>C and
 δ<sup>15</sup>N) and fungus comb C and N contents (C_cont,
 N_cont) are per mille (‰) and percentages (%), respectively. Geographic
 coordinates (x_coord, y_coord) are in WGS84 coordinate system. Nine
 different canopy cover estimates are percentages, e.g., column
 “cov100_over1” means coverage (%) of over 1 meter height vegetation at 100
 meters distance (circular buffer) from the mound centrum. For the MixSIAR analysis, source
 and discrimination tables are given in two separate files named
 <i>Source_table_C3C4.csv</i> and
 <i>Discrimination_table_C3C4.csv</i>, respectively<i>.
 </i>For SIBER analysis, three different subsets
 (<i>SIBER_site.csv, SIBER_termite.csv, SIBER_fungi.csv</i>)
 have been extracted from the principle data file, where the compared
 groups (study site, termite species, <i>Termitomyces
 </i>species) are coded with the following numbers: Sanctuary = 1,
 Mwashoti = 2, Maktau = 3, Mbula=  4, <i>M. subhyalinus </i>=
 1, <i>M. michaelseni </i>= 2, <i>Termitomyces
 </i>A = 1, <i>Termitomyces </i>C = 2. Observations from
 mounds where <i>Termitomyces </i>species could not be
 identified or groups had less than three individuals (colonies from study
 sites Latika and Mwashuma, or cultivating <i>Termitomyces
 </i>B) are omitted from the SIBER datasets. The fungus comb
 δ<sup>13</sup>C and δ<sup>15</sup>N are coded
 “iso1” and “iso2”, respectively.