The Lack of Knowledge Concerning the Empididae of Navarino Island

The Lack of Knowledge Concerning the Empididae of Navarino Island

            The flies of the family Empididae and the aquatic invertebrates of Navarino Island, Chile, are researched far less in comparison to other aquatic flies and vertebrate species, respectively. By studying the Empididae of Navarino Island, new information could be acquired both for the fields of taxonomy and freshwater ecology.

            The family Empididae is composed of small, predaceous flies, commonly referred to as “dance flies” due to their courtship displays. While not all of the species have aquatic life stages, around 660 species do have aquatic larvae and pupae (Wagner, 2008).  These aquatic larvae are important to their ecosystems both as predators and prey, feeding on smaller insects and being eaten by larger organisms. While these larvae have potential to be used as indicators for the health of the streams they live in, so few larvae have been linked to their adult forms that there is almost no way to identify them to the species level (MacDonald, 1999). Due to this, the family does not appear in nearly as much literature as other aquatic flies such as Chironomidae which are well described in all stages. Because this is coupled with the decline of taxonomists specializing in aquatic flies (Wagner, 2007), the family Empididae seems unlikely to be seen as useful for stream ecologists to study unless major developments are made in the identification of its species.
            Navarino Island, Chile, is part of the Cape Horn Biosphere Reserve and contains the Robalo watershed, one of the most pristine watersheds in the world (Anderson, 2007). This island contains the southernmost city in the world, Puerto Williams, and is considered to be in the sub-Antarctic ecoregion. While the vertebrates of the region, both native and invasive, have been heavily researched, little is currently known about the freshwater invertebrates (Moorman, 2006). This difference in attention may be attributed to the vertebrates being more “charismatic” and gaining the researchers more funding, but it creates problems due to the invertebrates typically playing a larger role in the healthy functions of streams than vertebrates do.

While the Empididae of the general area around Navarino Island area have been described (Collin, 1933), it has been a long time and the phylogeny of the family has greatly changed in recent years (Plant, 2011). The area is not predicted to have a large species diversity (Plant, 2011), and recent studies that identified down to the genus level found only one genera among several watersheds (Moorman, 2006). But, several new species have been identified in the last ten years around the world and it is possible that, due to the number of endemic aquatic insect species that are found in the area, some species of Empididae there may have been misidentified.

The matching of known adult species to their corresponding larvae could turn the Empidiade of the region into potential tools for stream quality assessment. It may be possible to match the adults and larvae using genetic tests, as this has been successful in the past (MacDonald 1999).Samples have been gathered for the last three years from the Robalo watershed to be analyzed and used as baseline data to compare against in the future (Contador, unpublished). If the Empididae from these samples can be identified to all developmental levels, they can be used as references for species diversity along with the better-known families.

Anderson, C.B. and Amy D. Rosemond, 2007. Ecosystem Engineering by invasive exotic beavers reduves in-stream diversity and enhances ecosystem function in Cape Horn, Chile. Ecosystem Ecology, 154: 141-153.

Collin, J. E., 1933. Diptera of Patagonia and South Chile, Based Mainly on Material in the   British Museum (Natural History); Part IV -- Empididae.

Contador, Tamara. Unpublished Material.

MacDonald, John F., and James R. Harkrider. Differentiation of Larvae of Metachela Coquillett and Neoplasta Coquillett (Diptera:Empididae:Hemerodromiinae) Based on Larval Rearing, External Morphology, and Ribosomal DNA Fragment Size. Journal of the North American Benthological Society 18: 414-419.

Moorman, M.C., C.B. Anderson, A. Gutiérrez, R. Charlin, & R. Rozzi, 2006. Watershed
conservation and aquatic benthic macroinvertebrate diversity in the Alberto D’Agostini
National Park, Tierra del Fuego, Chile. The Anales 34: 41-58.

Plant, Adrian R., 2011. Hemerodromiinae (Diptera: Empididae): a tentative

phylogeny and biogeographical discussion. Systematic Entomology, 36: 83-103.

Wagner, R., Bartàk, M., Borkent, A., Courtney, G., Goddeeris, B., Haenni, J.-P.,

Knutson, L., Pont, A., Rotheray, G.E., Rozkosny, R., Sinclair, B., Woodley, N.,

Zatwarnicki, T., Zwick, P., 2008. Global diversity of dipteran families (Insecta

Diptera) in freshwater (excluding Simulidae, Culicidae, Chironomidae, Tipulidae

and Tabanidae). Hydrobiologia 595, 489-519.

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This paper has been a challenge for me, mostly because of the lack of information out there about the region/family. That lack of information has become the topic of the paper, more or less, and I'm not sure if that's a good thing. If I can find more information in the next few weeks, this paper could change quite a bit. If not, I'll just be expanding on this.

Ecosystem Engineering by invasive exotic beavers reduces in-stream diversity and enhances ecosystem function in Cape Horn, Chile.

Anderson, C.B. and Amy D. Rosemond, 2007. Ecosystem Engineering by invasive exotic beavers reduces in-stream diversity and enhances ecosystem function in Cape Horn, Chile. Ecosystem Ecology, 154: 141-153.

Beavers were introduced to the Cape Horn region of South America during the early 20th century in order to start a fur industry. The industry didn't work out, but the beavers were well adapted to the region and soon expanded their territory throughout the islands. This study was done to find the effects beavers were having on stream ecosystems, including their effects on aquatic insects. In general, greater species diversity tends to equal greater productivity in ecosystems. In the beaver affected areas, however, the opposite was happening. The areas downstream of the beaver dams had fewer species of aquatic insects, but the overall numbers of insects were larger. The beavers changed the substrate of their streams by covering up the natural rock beds with organic debris. This destroyed the habitats for many insects, but allowed the insects that could live in the area to thrive due to the increase in nutrients. So while the beavers seemed to harm some species, they allowed the streams to have higher productivity due to increases in other areas. This further shows that exotic species can be complex issues.

The area the samples I'm studying came from is slightly affected by beavers. They have dams throughout the watershed, but the stream I care about is not directly downstream of them. If possible, I may be able to compare insects found at the source of the watershed, above any beaver sites, to the insects found at other sites.

Synopsis of the Hemerodromiinæ (Diptera, Empididæ)

This paper is a guide to the subfamily Hemerodromiinae found in North and South America. It includes two keys, one to the genus level for all of North and South America, and a much larger one for the species found in North and Central America. Each species is then given a paragraph in which all the external characteristics are described along with the general area they can be found in. The body parts whose features are most used to identify these flies are the antennae, genitals, wings, and front legs. Illustrations for the male genitalia for many of the species are included in tables at the end of the paper, showing their diversity and why they are useful identification tools.

This paper gave me a good starting point for what anatomical terms I’ll need to learn in order to identify these insects. It’s an old paper, and some species may have changed from then, but I doubt the terminology has. I’ll need to read more papers similar to this one to tell if the terms are consistent among authors.

Synopsis of the Hemerodromiinæ (Diptera, Empididæ)
Axel Leonard Melander
Journal of the New York Entomological Society, Vol. 55, No. 4 (Dec., 1947), pp. 237-273

Differentiation of Larvae of Metachela Coquillett and Neoplasta Coquillett (Diptera:Empididae:Hemerodromiinae) Based on Larval Rearing, External Morphology, and Ribosomal DNA Fragment Size

Flies in the family Empididae, while commonly found in aquatic environments, aren’t typically used as bio-indicators due to the difficulty in associating the adults, which are typically well-described, to the larvae which aren’t. This study attempted to associate larvae and adults in Utah and California by studying larvae morphology, rearing larvae and pupae, and observing ribosomal DNA fragments. For the DNA analysis, PCR was performed using the primers ITS 5 and RNA 2, which both target ribosomal genes. Gel Electrophoresis was then used to match the larvae with the adults and to differentiate between the genera. They found that the genera all created distinct enough bands to be able to tell them apart from each other, but it became more difficult at the species level for two of the genera. The species belonging to the genus Hemerodromia were easy to differentiate with electrophoresis, as were those of Chelifera.  The larvae of the different genera could be differentiated using morphology alone, and the researchers were able to update keys with better illustrations. They suggested that the primers used in the study could be used for other Hemerodromiinae to associate larvae with adults, or at the very least distinguish between genera.

This study outline possible steps I might take if I want to try to use genetic markers to associate larvae with adults. Hemerodromiinae is the sub-family I will probably be dealing with the most, and the genus Hemerodromia has appeared in other literature from the area my samples came from.

Differentiation of Larvae of Metachela Coquillett and Neoplasta Coquillett (Diptera:Empididae:Hemerodromiinae) Based on Larval Rearing, External Morphology, and Ribosomal DNA Fragment Size

John F. MacDonald and James R. Harkrider

Journal of the North American Benthological Society
Vol. 18, No. 3 (Sep., 1999), pp. 414-419

The conservation status of South American freshwater insects in the literature

The majority of conservation research and efforts are directed towards vertebrates, and research on aquatic invertebrates is especially underdeveloped.  By looking at the articles published in three important conservation journals from 1995 to 2008, it was possible to see exactly how little had been published on the topic of freshwater insects. Research done in all parts of the world had low percentages for this topic, but South America was the lowest with only .1% of the papers focusing on aquatic insect conservation. This seems problematic as freshwater ecosystems are considered some of the most endangered, and many aquatic insects are highly sensitive to changes in water quality. In the South American papers, there was an increase in papers dealing with the orders Ephemeroptera(mayflies), Trichoptera(stoneflies), and Odonata(dragonflies) over the years studied, so there does at least appear to be an increase in interest. In Chile, about 40% of taxonomists study vertebrates (1,700 species) while only 21% study insects (12,000 species). Part of this disparity could be linked to the overall “charisma” certain species have over others, as mammals and birds are usually seen as more important to conserve than insects, and among insects large butterflies and dragonflies are seen as more important to conserve than small gnats. This can be unfortunate as there are probably far more endangered insects than are recognized simply because no one has taken the time to study them.

This paper deals directly with why my project could be important for the region. I’ll be looking at extremely small flies that, while impressive under a microscope, probably fail to inspire much interest at first glance due to their size. The samples I’ll be looking at were taken from an extremely good-quality watershed. If the condition of the watershed changes in the future, it will be important to have a reference for what should be there.

Contador, Tamara . The conservation status of South American freshwater insects in the literature. Unpublished literature review.

Watershed Conservation and Aquatic Benthic Macroinvertebrate Diversity in the Alberto D'Agostini National Park, Tierra del Fuego, Chile

Moorman, M.C., C.B. Anderson, A. Gutiérrez, R. Charlin, & R. Rozzi, 2006. Watershed
conservation and aquatic benthic macroinvertebrate diversity in the Alberto D’Agostini National Park, Tierra del Fuego, Chile. The Anales 34: 41-58.

1. I will be looking at the species composition of a family of aquatic insects, most likely Empididae, from samples collected from the Robalo watershed near Puerto Williams, Chile. This will be done to find exactly which organisms are living there, because large scale identification has not been conducted in this particular watershed before.

2. The Cape Horn region of southern Chile has been declared both a biosphere reserve and a wilderness area, but before this study very little research had been done in the area to look at the conditions of the watersheds. Several watersheds in the D’Agostini National Park were picked as research locations and their water quality, surrounding vegetation, macroinvertebrates, human impact, and invasive species were recorded. Most of the watersheds were considered to be in pristine condition, and half had no sign of human impact. Introduced plant species and beavers were only found on the eastern side of the study area. Identifying the collected invertebrates to species was not a priority in this study, so many of the specimens are identified only to family or genus. By classifying the specimens into feeding groups, most of the insects were found to be dependent on the vegetation along the streams, which could lead to large changes in the composition if the natural vegetation were to be disrupted. Many endemic species were found, and it is likely there were more that have not been identified in a key yet. It was concluded that the watersheds in the park are still in very good condition, and the results found can be used to compare against future data in order to see how much the area has changed from its mostly pristine state.

3. This research was conducted in an area west of Navarino Island, where the samples I’ll be studying came from. Both regions are part of the Cape Horn Biosphere Reserve and have very similar native vegetation and potentially similar aquatic insects. They state in their study that many insects were not keyed to species because the keys did not exist for the, and I’ll probably run into this problem regardless of what family I research. The areas impacted by beavers are of particular interest, because almost all of the streams sampled in the Robalo watershed were downstream of areas beavers had built dams. I now have a better idea of what insects to expect to see in my research, down to genus level for most. This will help me find appropriate keys to start looking at.

The effects of substrate particle size on insect distribution and leaf decomposition

Reice, Seth R. 1980.The Role of Substratum in Benthic Macroinvertebrate Microdistribution and Litter Decomposition in a Woodland Stream. Ecology 11: 580-590.

Reice studied the relationship substrate size had with both the rate of leaf decomposition and aquatic insect distribution. This was done by creating baskets with three different sizes of substrate, covering half with leaf packs, placing them in the same area of a stream to reduce velocity variations, and sampling from them every two weeks for two months.

Leaf decomposition was the same for all three substrate groups at first, but by the end of the two months the substrate composed of cobbles, the largest used, had the most remaining leaf material. All leaf packs, regardless of their substrate, had about the same amount of insects inside them, meaning this was not a factor for the difference in decomposition. Insect density was greater on the leaves than on any of the substrates, and the presence of a leaf pack generally increased the density in the substrate below it. Preference over substrate size varied greatly by species, but density was overall higher in the largest substrate.

A strong aspect of this study is the fact that Reice managed to avoid the interrelatedness of current velocity and substrate particle size by studying patches of artificial substrate. This allowed him to view substrate preference as independent of preference for current speed. This study was conducted only during two months in the winter, and probably should have been repeated during other seasons to see if water temperature had any impact on the results.