Dennis R. Paulson

Global diversity of dragonflies (Odonata) in freshwater

Larvae of almost all of the 5,680 species of the insect order Odonata (dragonflies and damselflies) are dependent on freshwater habitats. Both larvae and adults are predators. The order is relatively well studied, and the actual number of species may be close to 7,000. Many species have small distributional ranges, and are habitat specialists, including inhabitants of alpine mountain bogs, seepage areas in tropical rain forests, and waterfalls. They are often successfully used as indicators for environmental health and conservation management. The highest diversity is found in flowing waters in rain forests of the tropics, the Oriental and Neotropical regions being the most speciose. This paper discusses diversity, summarises the biogeography of dragonflies in the different biogeographical regions and gives the total number of species and genera per family per biogeographical region. Examples are given of areas of particular diversity, in terms of areas of endemism, presence of ancient lineages or remarkable recent radiations but no well-based review of areas with high endemism of dragonflies is available so far. The conservation status of dragonflies is briefly discussed. Species confined to small remnants of forest in the tropics are most under threat of extinction by human activities.

The evolution and frequency of female color morphs in Holarctic Odonata: why are male-like females typically the minority?

Abstract We compiled data on the occurrence and frequency of distinct female variants among Holarctic Odonata and interpreted the data in light of harassment-based hypotheses. The major source of male confusion for male mimicry hypotheses is predicted to be signal similarity between andromorphs and male distractors; for the learned mate recognition hypothesis (LMR), it is predicted to be variation in female signals. Mapping morphism state onto molecular phylogenies of Ischnura and Enallagma failed to resolve the general ancestral female condition. However, it appeared that the andromorphic state may be ancestral in one case, and that blue structural colors were ancestral to orange and green pigmentations. Of the polymorphic species surveyed, 13% had more than two morphs, 4% had multiple heteromorphs but no andromorph, and 7% of ‘monomorphic’ congeners were functionally polymorphic because developmental variants mate. Such female signal variation lies beyond the scope of simple male mimicry, but nevertheless should exacerbate a males problem in searching for mates. Andromorphs were the majority morph in at least some populations of 17% of the species for which data were available. Andromorph frequencies of Enallagma species were generally higher than in Ischnura species, as expected if Ischnura andromorphs have higher signal apparency. Andromorph frequency varied significantly across habitats and species, as expected if per capita harassment and signal apparency vary among habitats. Quantification of signal apparency and per capita harassment across populations and among species is required to more rigorously test the extent to which variation in signal crypsis can explain observed variation in morph frequencies.

Population Structure in Overwintering Larval Odonata in North Carolina in Relation to Adult Flight Season

The hypothesis that North Temperate Odonata can be categorized into spring or summer species by the predominant overwintering instars and the position and duration of the adult flight season was tested for 55 species in North Carolina. Over 3,000 larvae of these species, collected at a time of stable instar distribution (winter), were examined and the population structure determined for each species. The composition of the wintering populations varied from a single instar to (probably) the entire spread of instars, known for the species. The peak occurred in any one of the last four instars, depending upon the species. The spring vs. summer species classification is valid at high latitudes but breaks down at the latitude of North Carolina, where there is a continuum of variance from one type of life history to another.

Recent Odonata records from southern Florida - effects of global warming?

Abstract A brief Odonata survey in southern Florida, USA, in January 2000 resulted in the discovery of two new species, Chrysobasis lucifer and Nehalennia minuta, for the USA and established populations of two other species, Tholymis citrina and Tramea calverti, that had been considered vagrants. Flight seasons of six additional species were extended. These records are discussed in light of the predicted effects of global warming.

Critical species of Odonata in the Neotropics

Abstract This report summarizes progress that has been made during the past five years toward the understanding of Neotropical Odonata. It also presents a list of critical species and sites, threats to Odonata conservation in the region, and priorities for further research. This region, the richest in the world for Odonata, must be a focus of intense research and conservation efforts.

Timeless standards for species delimitation

Recently a new species of bombyliid fly, Marleyimyia xylocopae, was described by Marshall & Evenhuis (2015) based on two photographs taken during fieldwork in the Republic of South Africa. This species has no preserved holotype. The paper generated some buzz, especially among dipterists, because in most cases photographs taken in the field provide insufficient information for properly diagnosing and documenting species of Diptera.

The Odonata of Pohnpei, Eastern Caroline Islands, Micronesia

Abstract A collection of 448 Odonata specimens made on Pohnpei, Caroline Islands, Micronesia, in 2001–2002 allows a reassessment of the fauna of this small, isolated island. There are 15 species, including six species of the zygopteran genus Teinobasis, which apparently speciated in situ, an unusually great diversity for such a small island. One of these species was undescribed. A revised key to the Teinobasis of Pohnpei is included, the larvae of three species of Teinobasis are compared, and the females of T. aerides and Pacificothemis esakii are described for the first time. The three odonate species represented by adequate series, T. ariel, T.fortis, and Hemicordulia haluco, appear to increase in body size with elevation. The island still has all of its natural habitats, although native upland forests continue to decrease as more land is cleared for agriculture. All of the odonate species seem secure at this time, although T. nigrolutea appears to be less common now than in the past.

Why do some zygopterans (Odonata) perch with open wings

Abstract Zygoptera show two perching modes, one with wings closed and one with wings open. These perching modes are distributed unequally through the suborder; most Zygoptera perch with closed wings, but species in 43 genera of eight families at least occasionally - in most cases usually - perch with open wings. Alternative hypotheses to explain this dichotomy are assessed. The dichotomy does not seem to be explicable by the Phylogenetic Inertia Hypothesis (PIH), the Wing Display Hypothesis (WDH), or the Thermoregulation Hypothesis (TH). I propose a hypothesis that the openwing position used by some zygopterans facilitates either more rapid takeoff or quicker orientation toward flying prey: the Quick Takeoff Hypothesis (QTH). That openwing species usually take flying prey furnishes support for the QTH, although many closedwing species also take flying prey. However, as most zygopterans perch with closed wings, that behavior needs explanation too, and I propose a hypothesis that perching with wings spread may make a zygopteran more conspicuous to predators and thus may be disadvantageous: the Shiny Wing Hypothesis (SWH). Larger species are less at risk of predation than smaller species, open wings in shade should be less conspicuous than in sunlight, and the majority of zygopterans with open wings are large tropical shade perchers, furnishing support for the SWH.

The Odonata of Kosrae, Eastern Caroline Islands, Micronesia

A recent collection of 69 specimens together with survey counts and incidental observations during June–July 2002 provide new information on the odonate fauna of Kosrae, Micronesia. The fauna comprises one zygopteran (Ischnura aurora) and six anisopterans. It appears to have remained stable with no known extinctions or colonizations over the past half century. The fauna is nearly a subset of that of Pohnpei and the islands to the west, and it comprises six widespread weedy species and one endemic, Hemicordulia erico. Upland aquatic habitats appear largely unexploited or underutilized by odonates, and the absence of any Teinobasis species on Kosrae is in marked contrast to the presence of six species on the nearest high island, Pohnpei.

Teinobasis budeni sp. nov. from Pohnpei, Eastern Caroline Islands, Micronesia (Odonata: Coenagrionidae)

Abstract Teinobasis budeni sp. nov. is described from Pohnpei, Federated States of Micronesia. Holotype ♂: Micronesia, Pohnpei, Sokehs, Nanpil River headwaters, 01 July 2001; allotype ♀: same locality, 03 February 2001, both leg. D.W. Buden; to be deposited in FSCA, Gainesville, FL, USA. The new species belongs in the Fortis-group and differs from all species in that group by characters of the male appendages, female ovipositor, hind prothoracic lobe, and coloration of immatures.