Dragonflies and Damselflies of New Zealand
168
Dragonflies and Damselflies of New Zealand
168eBook
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Product Details
| ISBN-13: | 9781776710430 |
|---|---|
| Publisher: | Auckland University Press |
| Publication date: | 07/18/2019 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 168 |
| File size: | 9 MB |
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CHAPTER 1
Natural History
This book includes those odonates so far established on New Zealand's four main islands as permanent or accidental residents. To date, 14 species are recognised as breeding in the North and South Islands, Stewart Island/Rakiura and the Chatham Islands. There are 11 genera, which are in turn grouped into six families.
Eight of these species are endemic – Austrolestes colensonis, Xanthocnemis tuanuii, X. zealandica, Uropetala carovei, U. chiltoni, Antipodochlora braueri, 'Procordulia' grayi and P. smithii. Four species (Ischnura aurora, Anax papuensis, Hemicordulia australiae and Tramea loewii) established breeding populations in New Zealand less than a hundred years ago. The remaining two (Aeshna brevistyla and Diplacodes bipunctata) are also found on other Pacific islands and in Australia; however, preliminary studies indicate that the New Zealand species have unique features that distinguish them to some extent from their overseas counterparts.
To make sense of New Zealand's odonates, we begin with a broad look at what these insects are and where they fit in the global classification of organisms living on our planet.
DAMSELFLIES AND DRAGONFLIES IN THE NATURAL WORLD
The branch of science called taxonomy deals with the naming and classification of living organisms. Scientists working in this field are taxonomists. They place organisms into hierarchically ranked groups or taxa (singular 'taxon'). At the lowest level, similar individuals that are capable of interbreeding and producing fertile offspring are categorised as being of the same species. Closely related species of common evolutionary origin that cannot interbreed form a genus. Similar genera are combined in a family, and the hierarchy continues as increasingly inclusive groups: order, class, phylum, kingdom and domain.
Since 1758, scientific names follow the binomial ('two-name') system of nomenclature devised by the Swedish naturalist Carolus Linnaeus. Every species is identified uniquely by its genus followed by its species name, as well as the name of the scientist who described the species and the year that description was published. The need for this is easy to see. There are, for example, many species named chiltoni, honouring the distinguished New Zealand zoologist Charles Chilton. These include worms, a fish, a snail, a crab and several insects. But the dragonfly Uropetala chiltoni Tillyard, 1921 is uniquely identified as a dragonfly of the family Petaluridae by its associated genus, as well as the fact that the description was published by the Australian entomologist Robert John Tillyard in 1921. The author and date are needed to establish priority in case another author should later publish the same name referring to a different species. If new information comes to hand and the species is later moved to another genus, the original author's name and date are placed in parentheses. Although all scientific names are nominally in Latin, they are frequently based on Latinised classical Greek or other languages (as in the chiltoni example, which is based on an English name).
Another advantage of an organism's scientific name being a unique combination of genus plus species is that it provides worldwide consistency, which is especially important for communication between scientists. Although common names may be easy to use, they can often cause confusion even among the native users. The term 'sandflies' illustrates this well. The annoying midges that New Zealanders call 'sandflies' are 'black flies' if you live in Britain or North America, but they all belong to the same family, Simuliidae. On the other hand, in Australia, 'sandflies' is the common name for equally annoying insects of a different family, Ceratopogonidae.
It bears pointing out, however, that non-scientific names have often been used to successfully distinguish between closely related species. Members of a tribe in Papua New Guinea recognise 137 out of the currently known 138 species of birds found in their area. The only two species they did not differentiate were very closely related.
Similar-looking species pose problems even for 21st-century taxonomists. Historically, species were classified using only morphological traits and they remain very important for identification and in describing new species. However, where morphological features are ambiguous, scientists use additional features based on the specimens' geographic distribution, behaviour and ecology. In recent years, taxonomists also compare the molecular structure of sections of the specimens' DNA. This has proved especially valuable in revealing higher-level relationships between groups, such as where a family should be placed, but it can also reveal 'cryptic' species – species that are almost impossible to differentiate by their outward appearance.
Turning specifically to the taxonomy of odonates, they belong to the kingdom Animalia, phylum Arthropoda, class Insecta. Collectively, insects represent the most successful lineage of multicellular organisms on the planet, both in numbers of individuals and diversity (numbers of species). In fact, the number of insect species greatly surpasses that of all other animal, plant and fungi species combined.
Insects are grouped into more than 30 orders. This book deals with just one, the order Odonata. The name of the order means 'toothed' and originates from the powerful serrated jaws (or 'mandibles') that are typical of all members of the group. Although Odonata is a comparatively small order of the Insecta (with just over 6000 extant species), the group has a very long evolutionary history. The oldest fossil record of a dragonfly dates back more than 250 million years and odonates' giant relatives – the Griffen-flies – date back 325 million years. Unfortunately, no fossil odonates have been found in New Zealand yet. This is a significant gap in our knowledge as fossils would tell us much about our past fauna and provide clues to understanding the present-day distribution of our species.
All New Zealand Odonata are divided into two suborders: Zygoptera and Anisoptera, which correspond to the common names 'damselflies' and 'dragonflies'. All our Zygoptera are small and light in build, and they rest with their wings folded together above the body, whereas our Anisoptera are larger, more heavily built and rest with their wings open. The two suborders differ in several other ways. In Zygoptera, the fore- and hindwings are almost identical, narrow and often stalked; Anisoptera have dissimilar wings that are broad at the base, especially the hindwing. They also differ in the terminal appendages of the male and in their naiads (this term, sometimes called a larva or nymph, refers to the period of life between egg and adult). Zygoptera naiads have slender and nearly parallel-sided bodies with three long, paddle-like gills (also known as 'lamellae' because of their thin, flat and often transparent layer). Anisoptera naiads are stouter, with laterally expanded abdomens, and they lack lamellae. Instead, their internal gills line the walls of the rectum, which can be sealed by closing small, spine-like projections on their abdomen.
Although Odonata comprises both damselflies and dragonflies, in recent years, 'odonates' or 'dragonflies' have been used widely when referring to all members of the order. In this book, whenever we speak of odonates, we mean the entire order Odonata. In some specific instances, we refer to the two suborders by their scientific names: Zygoptera and Anisoptera.
HABITATS OF NEW ZEALAND DAMSELFLIES AND DRAGONFLIES
New Zealand has a unique odonate fauna. Given the size of the two largest islands and the availability of good damselfly and dragonfly habitat (sites with poor drainage that can accumulate freshwater), New Zealand has surprisingly few species, all of which occur at relatively low abundance. In other parts of the world with a similar climate, most freshwater habitats sustain rich odonate communities, although there are progressively fewer species as one approaches the poles. Running and standing waters each provide a host of distinct habitats, supporting unique communities of naiads preferring different freshwater conditions. In the Northern Hemisphere, some species are especially adapted to live only in very harsh conditions, such as occur in bogs within the Arctic Circle where temperatures are very cold even during the summer, or in fast-running, shaded mountain streams passing through cool temperate forests. By contrast, New Zealand rivers and streams are almost devoid of odonates, a phenomenon that has never been fully explained. The geological and climatological history of the land undoubtedly had a significant impact on the evolution of local damselflies and dragonflies and the composition of the present fauna. The islands that form New Zealand today are the elevated remnants of a now mostly submerged continent, Zealandia. This large block of continental crust extends from the Subantarctic Islands to New Caledonia. About 84 million years ago, Zealandia began to separate from the Australian portion of the supercontinent Gondwana. Apart from Zealandia, Gondwana included what are now Australia, Antarctica, India, Africa, South America and some larger islands such as Sri Lanka and Madagascar.
With the break-up of Gondwana, its odonate fauna became fragmented and isolated on the separating land masses. We do not have fossil evidence to judge what share of species New Zealand received from the probably rich Gondwanan fauna. We can, however, assume that during the millennia of isolation, New Zealand's species were exposed to dramatic geological and climatic events. New Zealand travelled further south, taking warm-adapted species to a colder climatic zone. During the subsequent tens of millions of years, Zealandia's surface area was reduced to a few islands owing to the subsidence of a large part of the land. Most probably glaciation also took its toll, reducing further an already impoverished odonate fauna. The southern latitudes may have been more favourable for cold-tolerant insects such as stoneflies (order Plecoptera) and some mayflies (order Ephemeroptera), which develop predominantly in mountain streams. However, damselflies and dragonflies that occupy such habitats are mainly restricted to the tropics. Odonates found in temperate-zone mountains typically inhabit lakes and ponds.
In New Zealand, volcanic and tectonic activity raised some of the low-lying lakes (several of the present-day tarns), isolating the species in and around them from their lowland counterparts. Streams and rivers that originated on the newly raised slopes offered a wealth of new habitats. However, the species specialised to life in standing water probably were unable to occupy their unclaimed niches. It has been suggested that some populations of redcoat damselflies in the North Island may have invaded streams in shady forested areas and, over time, the descendants acquired morphological features which more than a hundred years ago were considered sufficient for them to be described as a separate species. Similarly, redcoat damselflies in the mountain tarns of the South Island are probably gradually differentiating from populations in the rest of the country. Unfortunately, with the lack of any fossils of dragonflies or dragonfly-like organisms, and no detailed comparisons between New Zealand species and those from the rest of the world, every theory is speculative at this stage. An integrated study involving several scientific disciplines is needed before we can begin to explain the paucity of odonates throughout New Zealand, especially in running water and in the South Island.
In fact, in running water habitats of the South Island, there are scarcely any species at all. The dusk dragonfly is the only New Zealand species with an affinity for flowing water and its distribution is limited to shady forest streams in the North Island. The redcoat damselfly may survive in slow-flowing rivers of the South Island, especially in areas where the water backs into small eddies along vegetated banks. Naiads of the ranger dragonfly have been found occasionally in running water in the South Island, but usually close to larger still-water basins from which they had most probably been flushed. That species also survives in North Island streams, but prefers sunnier sections than the dusk dragonfly and the redcoat damselfly. Unfortunately, our beautiful braided rivers do not support any viable odonate populations, as their ever-changing shape and rocky bottoms are not suitable for any of our present species.
Although both the redcoat damselfly and the ranger dragonfly can breed in running water, they are clearly far more abundant at ponds, lakes and other standing-water habitats. These species can even be found in lakes with slightly increased salinity, such as Brooklands Lagoon near Spencer Park, north of Christchurch. Coastal wetlands are also occupied by the blue damselfly and the red percher dragonfly, which may colonise very shallow and temporary pools, ponds and ditches. Freshwater lakes near the coast are good areas to find lancer and baron dragonflies. The freshwater allows the growth of a dense fringe of emergent vegetation and also supports floating plants, both of which provide perches for dragonflies and sites for egg-laying and emergence. Like the blue damselfly and the red percher dragonfly, the lancer dragonfly can breed in very shallow water.
Inland lakes (such as Rotoaira and Rotopounamu, near Taupo) with large areas of open surface water are attractive sites, especially for the yellow spotted dragonfly. The naiads live among submerged aquatic plants or on the lake bottom. Bank vegetation is also important to them for successful emergence. However, naiads do not depend on this entirely as adults sometimes emerge directly on rocks or fallen tree trunks near a bank. The yellow spotted dragonfly is also a common species in city gardens and at pools in recreational parks such as Otipua Wetlands, south of Timaru, and The Groynes Recreation Reserve, near Christchurch.
Some North Island ponds are dominated by the sentry dragonfly, which is gradually occupying larger territories in the South Island. Currently known as far south as Christchurch, this species may soon be recorded further south, especially with the present global trend of increasing annual temperatures. However, given its preference for warm habitats (adults have been observed patrolling over thermal streams near Rotorua, which were quite hot to touch), it is unlikely that the sentry dragonfly will ever establish at high elevations in South Island mountain tarns and peaty lakes. These areas are usually occupied by the redcoat damselfly, the blue damselfly and the ranger dragonfly.
Areas of open tussock grasslands with tiny water trickles flowing downhill are the habitat of the mountain giant dragonfly. Giant dragonflies are exceptional in that their naiads live in burrows dug into wet soils, usually densely overgrown with mosses and often far from any surface water. The size of the burrow depends on the naiad's stage of development, but they can be as deep as 70 cm. They may end in blind chambers or be U-shaped, thereby providing an alternate exit to escape a potential threat. The burrows are always partially inundated but are usually dry at the entrance, although in particularly wet soils the water level may reach almost to the burrow's opening. The naiads always keep the burrow clean – doing 'home maintenance' each night. Growing roots are nipped off, and collapsed soil is removed to a small pile at the entrance using the broad, flat mouthparts as shovels. Vacated burrows very soon became obliterated by growing roots and collapsing soil.
Adults of the mountain giant dragonfly are often encountered on some of New Zealand's more common alpine walks. Similarly, the bush giant dragonfly is also seen along walking tracks that pass through forested areas. Adults of this species tend to avoid open areas and prefer the shade of the trees. They may fly across forested clearings, but are rarely seen perching on completely exposed, sunlit vegetation.
(Continues…)
Excerpted from "Dragonflies and Damselflies of New Zealand"
by .
Copyright © 2019 Milen Marinov and Mike Ashbee.
Excerpted by permission of Auckland University Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
Preface,
Natural History,
Damselflies and dragonflies in the natural world,
Habitats of New Zealand damselflies and dragonflies,
Endemics and more recent arrivals,
Biology and behaviour,
Conservation,
Photographing damselflies and dragonflies,
Damselflies, dragonflies and communities,
Species Accounts,
Blue damselfly Austrolestes colensonis,
Gossamer damselfly Ischnura aurora,
Chatham redcoat damselfly Xanthocnemis tuanuii,
Redcoat damselfly Xanthocnemis zealandica,
Bush giant dragonfly Uropetala carovei,
Mountain giant dragonfly Uropetala chiltoni,
Lancer dragonfly Aeshna brevistyla,
Baron dragonfly Anax papuensis,
Dusk dragonfly Antipodochlora braueri,
Sentry dragonfly Hemicordulia australiae,
Yellow spotted dragonfly 'Procordulia' grayi,
Ranger dragonfly Procordulia smithii,
Red percher dragonfly Diplacodes bipunctata,
Common glider dragonfly Tramea loewii,
Species Likely to Establish,
Bibliography,
Acknowledgements,