Invasions by non-native ants are an ecologically destructive phenomenon affecting both continental and island ecosystems throughout the world. Invasive ants often become highly abundant in their introduced range and can outnumber native ants. These numerical disparities underlie the competitive asymmetry between invasive ants and native ants and result from a complex interplay of behavioral, ecological, and genetic factors. Reductions in the diversity and abundance of native ants resulting from ant invasions give rise to a variety of direct and indirect effects on non-ant taxa. Invasive ants compete with and prey upon a diversity of other organisms, including some vertebrates, and may enter into or disrupt mutualistic interactions with numerous plants and other insects. Experimental studies and research focused on the native range ecology of invasive ants will be especially valuable contributions to this field of study.

The Causes and Consequences of Ant Invasions

▪ Abstract Protective ant-plant interactions, important in both temperate and tropical communities, are increasingly used to study a wide range of phenomena of general interest. As antiherbivore defenses “worn on the outside,” they pose fewer barriers to experimentation than do direct (e.g., chemical) plant defenses. This makes them tractable models to study resource allocation to defense and mechanisms regulating it. As multi-trophic level interactions varying in species specificity and impact on fitness of participants, ant-plant-herbivore associations figure prominently in studies of food-web structure and functioning. As horizontally transmitted mutualisms that are vulnerable to parasites and “cheaters,” ant-plant symbioses are studied to probe the evolutionary dynamics of interspecies interactions. These symbioses, products of coevolution between plants and insect societies, offer rich material for studying ant social evolution in novel contexts, in settings where colony limits, resource supply, and ...

Protective ant-plant interactions as model systems in ecological and evolutionary research.

The incidence of phloem sap feeding by animals appears paradoxical. Although phloem sap is nutrient-rich compared with many other plant products and generally lacking in toxins and feeding deterrents, it is consumed as the dominant or sole diet by a very restricted range of animals, exclusively insects of the order Hemiptera. These insects display two sets of adaptations. First, linked to the high ratio of non-essential:essential amino acids in phloem sap, these insects contain symbiotic micro-organisms which provide them with essential amino acids. For example, bacteria of the genus Buchnera contribute up to 90% of the essential amino acids required by the pea aphid Acyrthosiphon pisum feeding on Vicia faba. Second, the insect tolerance of the very high sugar content and osmotic pressure of phloem sap is promoted by their possession in the gut of sucrase-transglucosidase activity, which transforms excess ingested sugar into long-chain oligosaccharides voided via honeydew. Various other animals consume phloem sap by proxy, through feeding on the honeydew of phloem-feeding hemipterans. Honeydew is physiologically less extreme than phloem sap, with a higher essential:non-essential amino acid ratio and lower osmotic pressure. Even so, ant species strongly dependent on honeydew as food may benefit from nutrients derived from their symbiotic bacteria Blochmannia.

Phloem-sap feeding by animals: problems and solutions

In this paper, the mutualistic relationship known as trophobiosis, which occurs convergently between ants and several groups of Hemiptera Sternorrhyncha and Auchenorrhyncha (formerly 'Homoptera') is reviewed. The main characteristics of 'Homoptera' and Formicidae which favor trophobiotic interactions, such as honeydew excretion by sap-sucking insects, ant attendance and physiological needs of both insects groups, are discussed. Aspects of the convergent evolution are presented. The most archaic system is not trophobiotic per se, foragers collect the honeydew casually expelled on the foliage by individuals or groups of non-associated 'Homoptera'. The commonest trophobiotic relationships are facultative; therefore, this form of mutualism is extremely diversified and is responsible for a range of physiological, morphological and behavioral adaptations by the 'Homoptera', mainly Sternorrhyncha. The more differentiated trophobioses are true symbioses where the most extreme changes can be observed on the 'Homoptera' side. Meanwhile, the ants show mainly behavioral adaptations resulting from a long coevolutive process. Considering the situation of sap-sucking insects as main crop pests worldwide, implications of trophobiotic relationships are discussed in the context of insect communities, in general, and on the problems that imply to Integrated Pest Management (IPM) in particular.

/pdf/trophobiosis-between-formicidae-and-hemiptera-sternorrhyncha-4i52j7btsc.pdf

Trophobiosis Between Formicidae and Hemiptera (Sternorrhyncha and Auchenorrhyncha): an Overview

We investigate the evolution of host association in a cryptic complex of mutualistic Crematogaster (De- cacrema) ants that inhabits and defends Macaranga trees in Southeast Asia. Previous phylogenetic studies based on limited samplings of Decacrema present conflicting reconstructions of the evolutionary history of the association, inferring both cospeciation and the predominance of host shifts. We use cytochrome oxidase I (COI) to reconstruct phylogenetic relationships in a comprehensive sampling of the Decacremainhabitants of Macaranga. Using a published Macaranga phylogeny, we test whether the ants and plants have cospeciated. The COI phylogeny reveals 10 well- supported lineages and an absence of cospeciation. Host shifts, however, have been constrained by stem traits that are themselves correlated with Macaranga phylogeny. Earlier lineages of Decacrema exclusively inhabit waxy stems, a basal state in the Pachystemon clade within Macaranga, whereas younger species of Pachystemon, characterized by nonwaxy stems, are inhabited only by younger lineages of Decacrema. Despite the absence of cospeciation, the correlated succession of stem texture in both phylogenies suggests that Decacrema and Pachystemon have diversified in association, or codiversified. Subsequent to the colonization of the Pachystemon clade, Decacrema expanded onto a second clade within Macaranga, inducing the development of myrmecophytism in the Pruinosae group. Confinement to the aseasonal wet climate zone of western Malesia suggests myrmecophytic Macaranga are no older than the wet forest community in Southeast Asia, estimated to be about 20 million years old (early Miocene). Our calculation of COI divergence rates from several published arthropod studies that relied on tenable calibrations indicates a generally conserved rate of approximately 1.5% per million years. Applying this rate to a rate-smoothed Bayesian chronogram of the ants, the Decacrema from Macaranga are inferred to be at least 12 million years old (mid-Miocene). However, using the extremes of rate variation in COI produces an age as recent as 6 million years. Our inferred timeline based on 1.5% per million years concurs with independent biogeographical events in the region reconstructed from paly- nological data, thus suggesting that the evolutionary histories of Decacrema and their Pachystemon hosts have been contemporaneous since the mid-Miocene. The evolution of myrmecophytism enabledMacarangato radiate into enemy- free space, while the ants' diversification has been shaped by stem traits, host specialization, and geographic factors. We discuss the possibility that the ancient and exclusive association between Decacremaand Macarangawas facilitated by an impoverished diversity of myrmecophytes and phytoecious (obligately plant inhabiting) ants in the region.

Codiversification in an ant-plant mutualism: stem texture and the evolution of host use in Crematogaster (Formicidae: Myrmicinae) inhabitants of Macaranga (Euphorbiaceae).

Myrmecophytic species of the Paleotropical plant genus Macaranga (Euphorbiaceae) have hollow stems that are almost always occupied by ants of the genus Crematogaster and scale insects of the family Coccidae (Hemiptera: Coccoidea). The coccids have a cryptic endophytic lifestyle and are confined to this microhabitat. They are much more diverse than previously recognised. First data are presented on the diversity, prevalence, specificity and distribution of the coccids associated with myrmecophytic Macaranga species. Twenty-two species of Coccidae in total, including 15 previously unknown from Macaranga, were disco- vered from 19 species of Macaranga in Peninsular Malaysia and Borneo. The ori- ginal describers tentatively assigned the known coccid species to Coccus (Coccinae) but the Macaranga coccids still require taxonomic research to establish their correct placing. The coccids varied in their host-plant specificity from species that occurred in most of the sampled Macaranga to one species that was found almost exclusively only on a single host species. In addition to their occurrence on Macar- anga, only three species, C. macarangae and C. secretus and morphospecies C. 214 were found on rare occasions in the stem interior of a few other myrmecophytes and in a non-myrmecophytic liana, but did not regularly colonise these plants. Most of the coccids can be regarded as highly specific at the plant genus level.

The soft scale (Coccidae) associates of Malaysian ant-plants

A trophobiotic relationship between two species of phloem-feeding plataspid bugs and an ant, Meranoplus mucronatus, was discovered on tree trunks in Malaysia. Similar relationships were found between coreid bugs and Crematogaster sp. and Anoplolepis longipes, on bamboo in the same area. The ants recruit to groups of the bugs and feed on the liquid, sugar-rich faeces of the larvae, stimulating release of the honeydew by tactile signals. They protect all stages of the bugs from disturbance by biting and by the use of defensive scretions. Phloem-feeding bugs in the families Plataspidae and Coreidae need long stylets to pierce the thick bark of their host tree. The different methods of accommodating the resting stylets in these two families are described. The plataspids are described as Tropidotylus servus sp. nov. and T. minister sp. nov. A coreid previously reported in association with M. mucronatus in Malaya is described as Hygia cliens sp. nov. The coreids on bamboo were determined as Cloresmus spp. and N...

/pdf/new-trophobiotic-symbioses-of-ants-with-south-east-asian-3nu2vhv4g8.pdf

New trophobiotic symbioses of ants with South East Asian bugs.

Within the paleotropical tree genus Macaranga (Thouars 1806) (Euphorbiaceae), the majority of ant-plant species are associated with specialized Crematogaster (Lund 1831) partner ants from the subgenus Decacrema (Myrmicinae). We have now discovered a completely different myrmecophytic system in which an ant species of the Formicinae lives in symbiosis with the peat swamp forest tree Macaranga puncticulata (Gage 1922). M. puncticulata twigs develop spacious cavities (domatia). An undescribed Camponotus (Colobopsis) (Mayr 1861) species of the C. saundersi-group was the dominant ant inhabitant (65% of the investigated plants) at forest sites, but this species, provisionally named C. (Colobopsis) sp. 1, was only rarely found at open stands. Another 29 opportunistic stem-nesting ant species were collected less frequently. None of them were Crematogaster (Decacrema) ants. C. (Colobopsis) sp. 1 has never been found to nest away from M. puncticulata. The mated queens are capable of locating young M. puncticulata p...

Camponotus (Colobopsis) (Mayr 1861) and Macaranga (Thouars 1806): a specific two-partner ant-plant system from Malaysia

The phytogeographic boundary Pattani-Kangar on the Malay Peninsula near the Malay-Thai boundary, between the evergreen rainforest and the Thai semi-evergreen rainforest, is the northern distribution limit of most myrmecophytic Macaranga associations. Only three myrmecophytic Macaranga species were found to occur along the northern distribution boundary of perhumid conditions: M. bancana, M. hypoleuca and M. griffithiana. We found no uninhabited plants there, suggesting that the distribution ranges of myrmecophytic Macaranga species and their associated Decacrema ants are largely concordant. Macaranga griffithiana was additionally found much further north in a disjunct area in continental eastern Thailand near Cambodia. It is the only myrmecophytic Macaranga species known to occur in the seasonally dry monsoon zone, which is possible because of exceptionally high rainfall in the so-called Chantaburi pocket. Here it is associated with a Camponotus (Colobopsis) species (Formicinae) instead of the typical southern Crematogaster (Decacrema) (Myrmicinae) partner ants. Also the endophytic trophobiotic scale insect partner differs from the species found in the southern populations. A new ant is described in this paper as Camponotus markli, belonging to the Colobopsis vitreus species group. This species, which is different from other known Camponotus plant-ant partners of Macaranga, is a specific partner of its plant, colonizing polydomously several trees and probably defending them against herbivores and climbers. The evolutionary implications of the disjunct distribution of Macaranga griffithiana and its partners are discussed. They are hypothesized to be relicts of larger former distribution ranges and of differing ancestor associations in former times. Accepted 28 April 2004.

https://www.soctropecol.eu/publications/pdf/10-1/Maschwitz,Fiala,Dumpert%20Ecotropica%202004.pdf

An unusual myrmecophytic macaranga association, occurring in a disjunct area in the monsoon zone of south-east asia: phenology and the description of a new ant species

The pioneer tree Macaranga in SE Asia has developed manyfold associations with ants. The genus comprises all stages of interaction with ants, from facultative relationships to obligate myrmecophytes. Only myrmecophytic Macaranga offer nesting space for ants and are associated with a specific ant partner. The nonmyrmecophytic species are visited by a variety of different ant species which are attracted by extrafloral nectaries (EFN) and food bodies. Transitional Macaranga species like M. hosei are colonized later in their development due to their stem structure. Before the colonization by their specific Crematogaster partner the young plants are visited by different ant species attracted by EFN. These nectaries are reduced and food body production starts as soon as colonization becomes possible. We demonstrated earlier that obligate ant partners can protect their Macaranga plants against herbivore damage and vine cover. In this study we focused on nonspecific interactions and studied M. tanarius and M. hosei, representing a non-myrmecophyte and a transitional species respectively. In ant exclusion experiments both M. tanarius and M. hosei suffered significantly higher mean leaf damage than controls, 37% versus 6% in M. hosei, 16% versus 7% in M. tanarius. M. tanarius offers both EFN and food bodies so that tests for different effects of these two food rewards could be conducted. Plants with food bodies removed but with EFN remaining had the lowest mean increase of herbivore damage of all experimental groups. Main herbivores on M. hosei were mites and caterpillars. Many M. tanarius plants were infested by a shootborer. Both Macaranga species were visited by various ant species. Crematogaster spp. being the most abundant. We found no eviB. Fiala (i:8J) . K.E. Linsenmair Lehrstuhl fUr Tierokologie und Tropenbiologie (Zoologie IJI), Biozentrum, Am Hubland, D-97074 Wiirzburg, Germany H. Grunsky . U. Maschwitz Zoologisches Institut, Siesmayerstrasse 70. D-60054 Frankfurt, Germany dence for any specific relationships. The results of this study strongly support the hypothesis that non-specific, facultative associations with ants can be advantageous for Macaranga plants. Food bodies appear to have lower attractive value for opportunistic ants than EFN and may require a specific dietary adaptation. This is also indicated by the fact that food body production in the transitional M. hosei does not start before stem structure allows a colonization by the obligate Crematogaster species. M. hosei thus benefits from facultative association with a variety of ants until it produces its first domatia and can be colonized by its obligate mutualist.

/pdf/in-macaranga-species-with-different-de-grees-of-ant-pozpi0vn2a.pdf

Ulrich Maschwitz

Papers

The soft scale (Coccidae) associates of Malaysian ant-plants

New trophobiotic symbioses of ants with South East Asian bugs.

Camponotus (Colobopsis) (Mayr 1861) and Macaranga (Thouars 1806): a specific two-partner ant-plant system from Malaysia

An unusual myrmecophytic macaranga association, occurring in a disjunct area in the monsoon zone of south-east asia: phenology and the description of a new ant species

in Macaranga species with different de,grees of ant association