Laurence A. Mound

Thysanoptera as Phytophagous Opportunists

The ecological concept of opportunism is defined, and its relevance to the biology of thrips and their ability to colonise ephemeral habitats is discussed. Evolutionary patterns in host-plant exploitation are explored, revealing that thrips generally adopt the dominant elements of a flora and are rarely constrained by host-plant systematic relationships. A few pest species are highly adaptable, feeding on leaf and flower tissue as well as being predators on other arthropods. Scarcely 1% of the 5,000 described species of thrips are serious pests, and most economic literature deals with just four species. Many more thrips are potential pests, and the contribution of various aspects of their biology to opportunism, such as voltinism, vagility, aggregation and reproductive effort, are considered, together with the relevance of this information to pest control strategies.

Thrips Pollination of the Central Australian Cycad, Macrozamia macdonnellii (Cycadales)

Macrozamia macdonnellii (Zamiaceae) grows at a few isolated sites in central Australia. Male cones support large populations of a host‐specific thrips, Cycadothrips albrechti n.sp. (Thysanoptera, Aeolothripidae). This insect breeds only in these male cones, from which the adults swarm in late afternoon as the temperature falls and humidity rises. A small sticky trap at one female cone caught 3844 adults on a single afternoon; large numbers of thrips were observed entering this cone. Each thrips carried an average of 15 pollen grains, and pollen delivery into the cone was thus estimated to average more than 5500 grains per ovule. No other potential pollinators were found on these cycads, and it is concluded that C. albrechti is the sole pollinator of M. macdonnellii. Since Cycadothrips constitutes a basal clade within the Thysanoptera, the possibility is considered that thrips were involved in pollen transfer before the radiation of flowering plants.

Taxonomy, Hypothesis Testing and the Biodiversity Crisis

The process of describing a new species is considered to be equivalent to generating a new hypothesis in other branches of biology. These hypotheses are falsified when descriptions are found subsequently to apply to species which have already been described; they are synonymized. A substantial proportion of all descriptions are subject to synonymy. This has profound implications for the amount of effort necessary to establish a foundation of descriptions of a given proportion of the world’s species, and hence for the practicality of some proposed responses to the biodiversity crisis. The patterns of synonymy of one order of insects, the Thysanoptera, through time and by authors, suggest some ways in which this problem may be reduced.

Identification, distribution and host-plants of the pest species of Scirtothrips (Thysanoptera: Thripidae).

Notes are given on the host range, distribution and recognition of the ten species of Scirtothrips recorded as pests: S. aurantii Faure on citrus in South Africa and bananas in Yemen; S. bispinosus (Bagn.) on tea in S. India; S. citri (Moult.) on citrus in California; S. dorsalis Hood on groundnuts in India, tea in Japan and strawberries in Queensland; S. inermis Priesn. on citrus in New Zealand; S. kenyensis Mound on tea in Kenya; S. longipennis (Bagn.) in glasshouses; S. mangiferae Priesn. on mango in Egypt and Israel; S. manihoti (Bondar) on cassava in Brazil; S. oligochaetus (Karny) on cotton in India. S. acaciae Moult, from Ghana is synonymised with S. aurantii Faure, and S. fragariae (Gir.) from Queensland is synonymised with S. dorsalis Hood. Drepanothrips reuteri Uzel, a grapevine pest from Europe and America which is very similar to Scirtothrips species, is newly recorded from Japan on Castanea .

Homoplasy and the delineation of holophyletic genera in some insect groups

Abstract. Some groups of insects, such as certain Ichneumonidae and fungus‐feeding Phlaeothripidae, appear to have undergone frequent reversal or parallelism (homoplasy) of characters during evolution so that extant species present almost every imaginable permutation and combination of characters. Recognition of holophyletic genera in such groups is difficult. Large monothetically defined genera are often not holophyletic, whilst small genera need to be defined by a large and invariable character‐suite. Any classification produced by adopting small genera will not possess one of the valuable attributes of the classical Linnaean system, its predictive ability; a large proportion of new species will require new genera. For groups exhibiting a high degree of homoplasy it is suggested that a polythetic classification be erected. Polythetic genera can be holophyletic groups and are not merely phenetic assemblages. The probability of correctly assigning a species (either a new one or when making an identification) is shown to be higher for a polythetic classification. A simple key device, the polyclave, is given to enable practical separation of two polythetic taxa. It is suggested that homoplasy, and its associated problems in classification, may be associated with a particular type of biology in which population size is not limited by direct competition.

Espécies de Frankliniella (Thysanoptera: Thripidae) de importância agrícola no Brasil

Six Frankliniella species: F. brevicaulis Hood, F. condei John, F. occidentalis (Pergande), F. schultzei (Trybom), F. williamsi Hood and F. zucchini Nakahara & Monteiro are pests in Brazil, three of them are virus-vector. A key to distinguish these species is provided, as well as their morphological characterization.

Thrips (Thysanoptera) pollination in Australian subtropical rainforests, with particular reference to pollination of Wilkiea huegeliana (Monimiaceae).

Approximately 23 species of thrips were recorded from flowers of 26 species of Australian subtropical rainforest trees, shrubs and vines (in 17 families) in the Manning Valley, coastal northern New South Wales. Pollination by thrips (thripophily) appears more widespread in rainforest communities than has been previously recognized. The pollination ecology of Wilkiea huegeliana (Monimiaceae) was studied in detail. Wilkiea huegeliana is a small, unisexual, annually flowering tree or shrub of rainforest and associated ecotones in eastern Australia, and is a larval food plant for the Regent Skipper butterfly Euschemon rafflesia rafflesia (Hesperiidae). At this latitude W. huegeliana is pollinated solely by a species of thrips, Thrips setipennis, but T. setipennis is not restricted to W. huegeliana and was recorded from flowers of 13 rainforest plant species. It appears to be the obligate pollinator also for Rapanea howittiana and R. variabilis (Myrsinaceae). Pollinator exclusion experiments were inconclusive but W. huegeliana may be facultatively agamospermous. The recruitment pathway to unrewarding female W. huegeliana flowers is uncertain but attraction may function by automimicry. Both male and female flowers serve as brood sites for T. setipennis larvae. Although the pollination ecology of W. huegeliana is specialized, the family Monimiaceae exhibits a broad diversity of pollination strategies. A number of these are discussed. The apparent obligate and restricted pollinator requirements of W. huegeliana may make it, and any associated phytophagous fauna, vulnerable to the impacts of habitat fragmentation.Approximately 23 species of thrips were recorded from flowers of 26 species of Australian subtropical rainforest trees, shrubs and vines (in 17 families) in the Manning Valley, coastal northern New South Wales. Pollination by thrips (thripophily) appears more widespread in rainforest communities than has been previously recognized. The pollination ecology of Wilkiea huegeliana (Monimiaceae) was studied in detail. Wilkiea huegeliana is a small, unisexual, annually flowering tree or shrub of rainforest and associated ecotones in eastern Australia, and is a larval food plant for the Regent Skipper butterfly Euschemon rafflesia rafflesia (Hesperiidae). At this latitude W. huegeliana is pollinated solely by a species of thrips, Thrips setipennis, but T. setipennis is not restricted to W. huegeliana and was recorded from flowers of 13 rainforest plant species. It appears to be the obligate pollinator also for Rapanea howittiana and R. variabilis (Myrsinaceae). Pollinator exclusion experiments were inconclusive ...

Phylogeny of thrips (Insecta: Thysanoptera) based on five molecular loci

The order Thysanoptera (Paraneoptera), commonly known as thrips, displays a wide range of behaviours, and includes several pest species. The classification and suggested relationships among these insects remain morphologically based, and have never been evaluated formally with a comprehensive molecular phylogenetic analysis. We tested the monophyly of the suborders, included families and the recognized subfamilies, and investigated their relationships. Phylogenies were reconstructed based upon 5299 bp from five genetic loci: 18S ribosomal DNA, 28S ribosomal DNA, Histone 3, Tubulin‐alpha I and cytochrome oxidase c subunit I. Ninety‐nine thrips species from seven of the nine families, all six subfamilies and 70 genera were sequenced. Maximum parsimony, maximum likelihood and Bayesian analyses all strongly support a monophyletic Tubulifera and Terebrantia. The families Phlaeothripidae, Aeolothripidae, Melanthripidae and Thripidae are recovered as monophyletic. The relationship of Aeolothripidae and Merothripidae to the rest of Terebrantia is equivocal. Molecular data support previous suggestions that Aeolothripidae or Merothripidae could be a sister to the rest of Terebrantia. Four of the six subfamilies are recovered as monophyletic. The two largest subfamilies, Phlaeothripinae and Thripinae, are paraphyletic and require further study to understand their internal relationships.

Natural and Disrupted Patterns of Geographical Distribution in Thysanoptera (Insecta)

Thrips are a frequent constituent of the aerial plankton and as a result the less host-specific species can disperse widely. Moreover, many are cryptic in behaviour and have been widely distributed through commercial traffic involving living plants, hay, dead wood, and the soil ballast of sailing ships. In recent years resolution of many taxonomic and systematic problems within this group of insects has revealed examples of natural vicariance as well as examples of disrupted distributions associated with major trading routes including the Atlantic slave trade and the New Zealand colonists. This review emphasizes the relationship between the biology of species and the ease with which they have been dispersed, as well as the diffilculty of recognizing natural distribution patterns in organisms so readily transported by winds.

Homologies and Host-Plant Specificity: Recurrent Problems in the Study of Thrips

ABSTRACT Precise studies on the structure and behavior of thrips can be particularly difficult, due to their small size and restless behavior. As a result, many “host-plant” records are no more than casual “finding places” with limited biological significance. Definitions of “host-plant” are complicated by situations where a plant species provides an important feeding or behavioral resource, but is not used for breeding. Similarly, failure to clearly define some structures on a thrips body, often due to inadequate technical and microscopy skills, can lead to faulty interpretation of species identities and evolutionary relationships. This article re-examines some of these problems.