The high canopy (33m-65m) from an ancient Sitka spruce forest in the Carmanah Valley on Vancouver Island, British Columbia, was investigated to examine the structure and diversity of the arthropod fauna. A fixed-access canopy system was developed to
facilitate arthropod sampling in this habitat.
Within the canopies of 5 ancient Sitka spruce trees, arthropods associated with branches were collected by cutting 270 branches over 6 time intervals. Branches were enclosed in plastic bags and contents were examined in the laboratory where 1,268 individuals were enumerated and assigned to feeding guilds. Arthropods associated with
the branches in the canopy were dominated by individuals in the phytophagous, predator and parasitoid guilds. Individual trees and seasonality both contributed significantly to the proportional structuring of the phytophagous and predator guilds. Vertical partitioning was not a significant factor in guild proportionality. Interaction effects were only significant for
the phytophagous guild. The documentation of high predator loading in a structurally and functionally diverse ecosystem such as ancient forest canopies is in concert with previous studies and supports observations on reduced herbivory in mature, structurally complex
forests. I suggest that canopy habitats provide a template important for examining questions about the maintenance of biodiversity in ancient forests. Further understanding of the factors involved may provide us with predictive information that could be used to
examine patterns in community structure and provide answers to process-driven biodiversity and conservation questions.
I collected samples bi-weekly throughout the growing season, from replicated moss/soil samples and malaise traps from 5 study sites associated with the ancient Sitka spruce forests: 2 ancient forest Sitka spruce canopies, ancient forest interior, transition zone
(edge between ancient forest and clear-cut), and clear-cut (6 years old). I recorded 71 species of Oribatida ( 2,117 specimens), representing 51 genera and 34 families. Taxonomic distincness was most pronounced in the canopy moss/soil mats where oribatid mites are members of a distinct arboreal community that is not just a random sub-set of the ground fauna. Comparisons between the high-canopy and three ground sites indicated that overall, species percent similarity was low. Thirty and 28 species of oribatids were
recorded from the 2 canopy sites, of which 12 species are canopy specific. Species exhibiting strict arboreal specificity are all in the Brachyphlina, from the families Thyrisomidae, Damaeidae, Eremaeidae, Oripodidae, Gymnodamaeidae,Oppiidae,Peloppiidae, Galumnatidae, and Cymbaeremaeidae. I consider oribatids of the canopy to be inhabitants of islands, in the sense that they are isolated from their ground coimterparts and have a distinct fauna that is characterized by two ecological groups of species;
wandering species with dispersal capabilities and arboreal species with low dispersal capabilities. I conclude that oribatid mites can be used as a surrogate for other ancient forest soil microarthropods, and predict that arboreal specificity will also be pronounced in
these taxa.
I explored dispersal capabilities further, where 36 species of Oribatida (2596 specimens), representing 29 genera and 21 families were recorded from replicated malaise traps positioned in the canopy and on the forest floor. Colonization of malaise traps was
100% in the canopy, 91% in the forest floor and 47% in the clear-cut.Nine of these species were not recorded using high gradient extractions of moss/sod from the canopy or forest floor or clear-cut. Thirty of these species are Brachypyiina, with the families
Eremaeidae, Peloppiidae and Ceratozetidae represented by three or more species. Colonizing specimens were predominantly adult, and represent sexually vreproducing taxa; immatures comprised only 0.9% to 4.2% of specimens. Ceratoppia spp., Eporibatula sp.1, Dorycranosus sp.l, Sphaerozetes sp. 1 and Oribatella sp. 1 had a ftequency > 50% in the forest floor malaise traps, and Eporibatula sp. I, Sphaerozetes sp.
1 and Dendrozetes sp. 1 had a frequency > 50% in canopy malaise traps. Phoresy as a source of the oribatid fauna in the malaise traps is unlikely as only Paraleius sp. 1 of the species represented is modified for this mode of dispersal. The number of species recorded from malaise traps, and the frequency, relative abundance and seasonality of many of them support the hypothesis that active aerial dispersal by random movement is an important mode of colonization of canopy habitats.
I examined features related to the Centinelan extinction concept and asked whether or not this is applicable to northern temperate ancient forest arthropods. Habitat loss in these forest systems on Vancouver Island is well documented and at present, of 89 ancient
forest watersheds over 5000 ha in size, only 6 remain undisturbed by logging. Examination of identified arthropod species ( 1,311 to date), indicates that the structurally complex habitat acts as a reservoir for biological diversity. Of particular importance to the
maintenance of arthropod biodiversity is the documentation of those species that are new to science or species that are restricted to habitats only found in ancient forests. The new species (approx. 120) so far recorded represent a contribution towards categorizing the
endemic arthropod fauna of this ancient forest. I expect that, with continued taxonomic resolution, this list of undescribed species will be significantly increased. Specific examples include Hypogastrura arborea Fjellberg, Anacliliea vallis Coher and A winchesteri Coher, Cinara n. sp. Voegtlin, and Miniliomosina n. sp. Marshall. This type
of habitat specificity is well documented for the oribatid mites and for the staphylinid beetles where I have documented 8 new species of Omaliinae which appear to rely on ancient forests as a source area to maintain reproductively viable subpopulations. Without proper documentation, I suggest that the arthropod fauna of ancient forests contain species that are candidates for the Centinelan extinction concept — extinction of species unknown before their demise and hence unrecorded.
In conclusion, my studies present evidence from several arthropod groups to indicate that the ancient forests of the Carmanah Valley act as a source habitat for several species, many of which are currently undescribed. Habitat specificity is most pronounced in the
canopy where soil micro-arthropods such as the oribatid mites exhibit arboreal specificity. The importance of describing these species assemblages coupled with the inclusion of dynamic processes such as dispersal into the framework of how we think about arthropods in ancient forests is a challenge that lies ahead for the entomological research community. Recognizing these components should assist efforts in addressing the conservation of biodiversity in these ancient forests. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/8433 |
| Date | 18 August 2017 |
| Creators | Winchester, Neville Norman |
| Contributors | Ring, Richard A. |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
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