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opencc-zeroSep 2019View details →

Data from: The molecular phylogenetics of Trachymyrmex ants and their fungal cultivars provide insights into the origin and co-evolutionary history of 'higher-attine' ant agriculture

The fungus‐growing ants and their fungal cultivars constitute a classic example of a mutualism that has led to complex coevolutionary dynamics spanning c. 55–65 Ma. Of the five agricultural systems practised by fungus‐growing ants, higher‐attine agriculture, of which leaf‐cutter agriculture is a derived subset, remains poorly understood despite its relevance to ecosystem function and human agriculture across the Neotropics and parts of North America. Among the ants practising higher‐attine agriculture, the genus Trachymyrmex Forel, as currently defined, shares most‐recent common ancestors with both the leaf‐cutter ants and the higher‐attine genera Sericomyrmex Mayr and Xerolitor Sosa‐Calvo et al. Although previous molecular‐phylogenetic studies have suggested that Trachymyrmex is a paraphyletic grade, until now insufficient taxon sampling has prevented a full investigation of the evolutionary history of this group and limited the possibility of resolving its taxonomy. Here we describe the results of phylogenetic analyses of 38 Trachymyrmex species, including 27 of the 49 described species and at least 11 new species, using four nuclear markers, as well as phylogenetic analyses of the fungi cultivated by 23 species of Trachymyrmex using two markers. We generated new genetic data for 112 ants (402 new gene sequences) and 95 fungi (153 new gene sequences). Our results corroborate previous findings that Trachymyrmex, as currently defined, is paraphyletic. We propose recognizing two new genera, Mycetomoellerius gen.n. and Paratrachymyrmex gen.n., and restricting the continued use of Trachymyrmex to the clade of nine largely North American species that contains the type species [Trachymyrmex septentrionalis (McCook)] and that is the sister group of the leaf‐cutting ants. Our fungal cultivar phylogeny generally corroborates previously observed broad patterns of ant–fungus association, but it also reveals further violations of those patterns. Higher‐attine fungi are divided into two groups: (i) the single species Leucoagaricus gongylophorus (Möller); and (ii) its sister clade, consisting of multiple species, recently referred to as Leucoagaricus Singer 'clade B'. Our phylogeny indicates that, although most non‐leaf‐cutting higher‐attine ants typically cultivate species in clade B, some species cultivate L. gongylophorus, whereas still others cultivate fungi typically associated with lower‐attine agriculture. This indicates that the attine agricultural systems, which are currently defined by associations between ants and fungi, are not entirely congruent with ant and fungal phylogenies. They may, however, be correlated with as yet poorly understood biological traits of the ants and/or of their microbiomes.

opencc-zeroJun 2022View details →

Cold tolerance of Trachymyrmex fungus gardening ants and Leucocoprinus symbionts

Symbionts can have profound effects on host fitness, adaptations, and range distributions. Stress-induced evolution is difficult to show in obligate symbioses, however, adaptive evolution within an obligate symbiosis can be investigated experimentally or by correlating trait variation with stress along an ecological cline (i.e., temperature-stress gradient). We investigated the cold-tolerance of the fungus-growing ant Trachymyrmex septentrionalis by performing cold-tolerance assays comparing two populations collected from either the southernmost range of their distribution (Bastrop, TX) or from a site that is approximately 600 km further north (Norman, Oklahoma). We first compared isolated fungal symbionts grown on artificial media to determine cold-tolerance of fungus alone. Subsequently, we conducted cross-fostering experiments between northern and southern host and symbionts to test for synergisms between the partners in generating adaptations of cold tolerance. Ants of the northern fungal populations were more cold-adapted then southern fungal populations. Northern nests were deeper and northern colonies initially rejected fungi from the southern population. The cross-fostering experiments demonstrated that only one partner must be cold tolerant to confer maximum cold-tolerance to the ant-fungus symbiosis, because northern ants growing southern fungus under cold stress performed just as well as northern ants growing northern fungi. Our results suggest that cold stress has been an important selective factor during the migration of this ant-fungus symbiosis into northern latitudes during the last 10,000 years, and that cold tolerance likely is an energetically demanding trait that may be traded off with other aspects of the symbiosis' life history. The symbiosis also appears to have evolved several additional adaptations that increase survival in cold environments, such as building deeper nests that insulate the fungi from cold surface

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Fig. 1 in Geographic distribution of Trachymyrmex jamaicensis (Hymenoptera: Formicidae)

Fig. 1. Known site records of Trachymyrmex jamaicensis.

opencc-by-4.0Dec 2015View details →

publicSep 2019View details →

Data from: The molecular phylogenetics of Trachymyrmex ants and their fungal cultivars provide insights into the origin and co-evolutionary history of 'higher-attine' ant agriculture

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publicJun 2022View details →

Cold tolerance of Trachymyrmex fungus gardening ants and Leucocoprinus symbionts

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FIGURE 20 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 20: Trachymyrmex turrifex male in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 2 mm, 1 mm and 2 mm in part (a), (b) and (c), respectively.

FIGURE 19 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 19: Trachymyrmex turrifex worker in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm, 0.5 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 21 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 21: Maximum Likelihood phylogram of surveyed populations of the Trachymyrmex species occurring in the United States, with branch lengths, calculated under GTR+R model. Numbers on branches represent bootstrap values based on 560 pseudoreplications. The scale bar depicts expected rate of substitutions per site. County/Parish, State and Country names (for Mexican samples) are given behind the species name. Note: the taxon sampling for the genus Trachymyrmex is incomplete, thus two species appearing adjacently in this phylogram are not necessarily sister taxa.

FIGURE 18 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 18: Trachymyrmex smithi male in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 2 mm, 1 mm and 2 mm in part (a), (b) and (c), respectively.

FIGURE 2 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 2: Trachymyrmex arizonensis male in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 2 mm, 1 mm and 2 mm in part (a), (b) and (c), respectively.

FIGURE 1 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 1: Trachymyrmex arizonensis worker in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm, 0.5 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 13 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 13: Trachymyrmex pomonae Paratype queen in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm, 0.5 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 9 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 9: Trachymyrmex jamaicensis male in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm, 0.5 mm and 0.5 mm in part (a), (b) and (c), respectively.

FIGURE 17 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 17: Trachymyrmex smithi worker in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm, 0.5 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 5 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 5: Trachymyrmex desertorum worker in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm, 0.5 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 16 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 16: Trachymyrmex septentrionalis male in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 2 mm, 1 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 12 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 12: Trachymyrmex pomonae Holotype worker in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm, 0.5 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 7 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 7: Trachymyrmex desertorum male in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 2 mm, 1 mm and 1 mm in part (a), (b) and (c), respectively.

FIGURE 8 in A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae)

FIGURE 8: Trachymyrmex jamaicensis worker in (a) lateral, (b) full face and (c) dorsal view. Scale bar represents 1 mm in each part of the figure.