The arthropods are vast in terms of species, and include ants, beetles, butterflies, mites, moths, spiders, and so on. Therefore, covering the entire spectrum of arthropods in this section is impractical, though the general provisioning by trees will be outlined and species will be used to illustrate given examples.
Many arthropods are considered to be saproxylic in nature – they principally utilise dead woody material (both standing and fallen, in both dead and living trees) as habitat, for at least part of their life cycle, though they may also rely upon fungal sporophores associated with the presence of deadwood, as is to be detailed below (Gibb et al., 2006; Harding & Rose, 1986; Komonen et al., 2000). Of all the saproxylic arthropods, beetles are perhaps the most significant in terms of the proportion occupied of total saproxylic species worldwide (Müller et al., 2010), though saproxylic flies also feature in great numerical abundance (Falk, 2014; Harding & Rose, 1986).
Beetles may be either generalist or specialist in nature (on either broadleaved or coniferous hosts), and they will normally require a host with an abundance of deadwood (or large sections of coarse woody debris) usually over 7.5cm in diameter that resides within an area typically not heavily shaded (Müller et al., 2010; Siitonen & Ranius, 2015). This may be, in part, due to many beetle species (in their adult stage) requiring nectar from herbaceous plants, which would be lacking in woodland with significant canopy closure (Falk, 2014; Siitonen & Ranius, 2015). This means that veteran trees amongst wood pasture and parklands (including in urban areas) may be particularly suitable (Bergmeier & Roellig, 2014; Harding & Rose, 1986; Ramírez-Hernández et al., 2014; Jonsell, 2012; Jørgensen & Quelch, 2014), though this is not at all a steadfast rule as species may also be found abundantly in (perhaps more open) woodland, and particularly where there are large amounts of veteran trees and deadwood – around 60 cubic metres per hectare, according to Müller et al. (2010). Granted, they are found particularly in older (mature to veteran) trees, including within cavities that possess wood mould, water-filled rot holes, dead bark, exposed wood, sap flows, fruiting bodies (of fungi and slime moulds), mycelia of fungi, dead branches, and dead roots (Carpaneto et al., 2010; Falk, 2014; Harding & Rose, 1986; Siitonen & Ranius, 2015; Stokland et al., 2012). Beetle species may also not necessarily associate preferentially with a species (or group of species), but with the conditions aforementioned that are present within a tree (Harding & Rose, 1986; Jonsell, 2012). At times, preferable conditions may be an infrequent as one veteran tree in every hundred (Harding & Rose, 1986).
Despite this, species preference is observed. For broadleaved obligates, heavier shade may be more necessary, and in such instances there is a closer affinity of the beetles with fungal mycelium. Because fungi tend to produce more mycelium in cooler and more humid conditions (though this does, of course, vary with the species), the broadleaved obligates may therefore be found normally in greater abundance where conditions are more suited to fungal growth, and their presence may thus be associated with a canopy openness of as little as 20% (Bässler et al., 2010; Müller et al., 2010). This is, of course, not a steadfast rule, and many open wood pastures may support a great abundance of saproxylic beetles (Harding & Rose, 1986).
It is also important to recognise that many species of saproxylic beetle are reliant upon particular stages of the wood decay process. For instance, species that require fresh phloem tissue will only be able to colonise briefly in the first few summers following on from the death of the phloem tissue (Falk, 2014). Other species require significantly-decayed wood in a particular micro-climate, and even of a particular tree species (Harding & Rose, 1986). There also exist intricate associations between species of fungi and saproxylic insects. Inonotus hispidus, which is usually found upon ash, is the habitat for Triplax russica and Orchesia micans, whilst the coal fungus (Daldinia concentrica), also oft found upon the deadwood of ash (Fraxinus excelsior), is the main provider of habitat for Platyrhinus resinosus (Falk, 2014). The birch polypore (Fomitopsis betulina) is also host to numerous species of Coleoptera (Harding & Rose, 1986); as is the polypore Fomitopsis pinicola (Jonsson & Nordlander, 2006; Komonen, 2003; Komonen et al., 2000). This means that these species may be found where there is a suitable population of the fungus’ host species, where sporophores are present and will likely fruit again in the future, across numerous trees, and for many years. Most beetle species rely on oak more so than other tree species however, as oak generally lives for much longer and thus provides a wider array of different micro-habitats, and possesses increased compositional complexity as a result (Harding & Rose, 1986; Siitonen & Ranius, 2015).
Therefore, the loss of suitable habitat through active management programmes (including logging, and felling trees for safety reasons in urban areas) will have a very adverse impact upon saproxylic beetles, though also certain species of moth, and even species associated with saproxylic insects, including parasitic wasps, solitary wasps (which use beetle bore holes for habitat), and predatory Coleoptera (Harding & Rose, 1986; Komonen et al., 2000). Curiously, research by Carpaneto et al. (2010) concluded that trees that were ranked as the most evidently ‘hazardous’ were host to the most saproxylic beetle species, and their removal would therefore have a drastic impact upon local populations. Similarly, fragmentation of woodland patches suitable for saproxylic populations has led to a decline in the meta-populations (Grove, 2002; Komonen et al., 2000), as has deadwood removal in a managed site itself (Gibb et al., 2006). Interestingly, though not surprisingly, ‘deadwood fragmentation’ also has an adverse impact upon saproxylic insect populations (Schiegg, 2000).
Both ants and termites also benefit from the presence of deadwood. With regards to both, nests will usually form at the base of a tree or at an area where there is at least moderate decay – enough to support a viable population (Jones et al., 2003; Shigo, 1986; Stokland et al., 2012). Ants and termites both follow CODIT (compartmentalisation of damage in trees) patterns in relation to how their nests progress, and thus their territory will increase as fungal decay propagates further into the host. Ants will not feed on the decaying wood of the host however, and will simply use the decaying site as a nesting area. Conversely, termites will feast upon decayed wood and essentially control (perhaps by slowing down) the spread of fungal decay in a manner that provides as much longevity of the host as possible for a viable nesting site (Shigo, 1986). In tropical rainforests, termites are in fact considered to be one of the principal means of wood decomposition (Mori et al., 2014), and thus the provisioning of deadwood habitat is absolutely critical. Without decaying wood within trees therefore, ants and particularly termites will lack a potential habitat, and thus where a stand is actively managed populations may be markedly reduced (Donovan et al., 2007; Eggleton et al., 1995). Of course, termites are not necessarily to be desired when they are invading the wood structure of a property, and therefore deadwood is not universally beneficial (Esenther & Beal, 1979; Morales-Ramos & Rojas, 2001) – at least, when human properties are involved.
The presence of deadwood may also be beneficial for ground-nesting and leaf-litter dwelling spiders, which can utilise downed woody debris (particularly pieces with only slight decay) for both nesting and foraging (Varady-Szabo & Buddle, 2006). In fact, research by Buddle (2001) suggested that such spiders may more routinely utilise downed woody material when compared to elevated woody material (dead branches and telephone poles) because of the greater array of associated micro-habitats, and particularly at certain life stages – such as during egg-laying, for females (Koch et al., 2010). Furthermore, as fallen woody debris can help to retain leaf litter (or even facilitate in the build-up leaf litter), spider populations are more abundant and more diverse in sites where such woody debris is present (Castro & Wise, 2010). Therefore, where woodlands are managed and areas are clear-cut, spider populations may be markedly reduced in terms of the diversity of species. However, generalist species may benefit from the amount of cut stumps (Pearce et al., 2004). Curiously, Koch et al. (2010) suggest that spiders may perhaps benefit from woodland clearance, because the vigorous re-growth of trees and the higher light availability to the woodland floor (promoting herbaceous plant growth) increases the abundance of potential prey. Despite this, old-growth species will suffer (Buddle & Shorthouse, 2008), and thus the population structure of spider populations may dramatically change.
Soil mites are a further group that benefit from coarse woody debris, though also from hollows and holes throughout the basal region of a tree (including water-filled cavities), and from fungal sporophores and hyphae associated with wood decay (Fashing, 1998; Johnston & Crossley, 1993). Typically, termites will use fungi and insects found within the wood as a food source, and the wood structure itself will provide for an array of niche micro-habitats that are critical at different life stages of a mite. Certain mite species are obligates that associate with coarse woody debris exclusively, and may in fact only be associated with certain species’ woody debris. Additionally, mites may utilise woody debris and hollows within trees to parasitise upon other species using the ‘resource’, with both lizards and snakes being parasitised by mites following their frequenting of such resources. Beetles may also be parasitised, though the mite in such an instance may use the beetle as a means of entry into woody debris (Norton, 1980).
It is not just deadwood that arthropods will utilise, however. Foliage, both alive and abscised, is also of use (Falk, 2014). For example, the ermine moth (Yponomeutidae) will rely upon the living foliage of a host tree as a food source, and the bird cherry ermine moth (Yponomeuta evonymella) is one example of this. During late spring, larvae will fully defoliate their host Prunus padus, before pupating, emerging, and then laying eggs upon the shoots ready for the following year (Leather & Bland, 1999). Many other moth species will, during their larval stage, also behave in such a manner and thus defoliate their host – either entirely, or in part (Herrick & Gansner, 1987). Other species may alternatively have larvae mine into the leaf and feed upon the tissues within (Thalmann et al., 2003), such as horse chestnut leaf miner (Cameraria ohridella). Flies, including the holly leaf-miner (Phytomyza ilicis), will also mine leaves in a similar fashion (Owen, 1978). Ultimately however, the same purpose is served – the insect uses the living tissues of a leaf to complete its life cycle, and fuel further generations.
Fallen leaf litter, as briefly touched upon earlier when discussing spiders, may also be of marked benefit to many arthropods. Ants, beetles, and spiders are but three examples of groups that will utilise leaf litter as a means of habitat (Apigian et al., 2006). Beetles will, for instance, rely upon leaf litter to attract potential prey, though also to provide niche micro-climates that remain relatively stable in terms of humidity, light availability, and temperature (Haila & Niemelä, 1999). Their abundance may, according to Molnár et al., (2001) be greatest at forest edges, perhaps because prey is most abundant at these edge sites (Magura, 2002). Of course, this does not mean that edges created through artificial means will necessarily improve beetle populations, as research has shown that there are few ‘edge specialists’ and therefore populations usually will go into decline where there has been significant disturbance. Unless management mimics natural mortality events of forest trees, then constituent beetle populations may thus suffer adversely (Niemelä et al., 2007).
With regards to ants, Belshaw & Bolton (1993) suggest that management practices may not necessarily impact upon ant populations, though if there is a decline in leaf litter cover then ants associated with leaf litter presence may go into – perhaps only temporary (until leaf litter accumulations once again reach desirable levels) – decline (Woodcock et al., 2011). For example, logging within a stand may reduce leaf litter abundance for some years (Vasconcelos et al., 2000), as may (to a much lesser extent) controlled burning (Apigian et al., 2006; Vasconcelos et al., 2009), though in time (up to 10 years) leaf litter may once again reach a depth suitable to support a wide variety of ant species. However, the conversion of forest stands into plantations may be one driver behind more permanently falling ant populations (Fayle et al., 2010), as may habitat fragmentation (Carvalho & Vasconcelos, 1999) – particularly when forest patches are fragmented by vast monoculture plantations of tree or crop (Brühl et al., 2003). The conversion of Iberian wood pastures to eucalyptus plantations is one real world example of such a practice (Bergmeier & Roellig, 2014).
Also of benefit to many arthropods are nectar and pollen. Bees, beetles, butterflies, and hoverflies will, for instance, use nectar from flowers as a food source (Dick et al., 2003; Kay et al., 1984), and generally (but not always) a nectar source will lack significant specificity in terms of the insect species attracted (Karban, 2015). Despite this, different chemicals secreted by different flowers, and the toxicity of certain nectar sources to particular insects, means certain tree species may only be visited by certain insect species (Adler, 2000; Rasmont et al., 2005). Tree diversity may therefore be key to sustaining healthy insect populations (Holl, 1995), and where species may prefer to frequent herbaceous plant species the presence of a diverse woodland canopy above may still be very influential (Kitahara et al., 2008). This may be because a diverse array of woody plant species increases the diversity of herbaceous species. At times, pollen may also be a reward, as may (more rarely) a flower’s scent. Karban (2015) remarks that all are collectively dubbed as ‘floral rewards’.
Adler, L. (2000) The ecological significance of toxic nectar. Oikos. 91 (3). p409-420.
Apigian, K., Dahlsten, D., & Stephens, S. (2006) Fire and fire surrogate treatment effects on leaf litter arthropods in a western Sierra Nevada mixed-conifer forest. Forest Ecology and Management. 221 (1). p110-122.
Bässler, C., Müller, J., Dziock, F., & Brandl, R. (2010) Effects of resource availability and climate on the diversity of wood‐decaying fungi. Journal of Ecology. 98 (4). p822-832.
Belshaw, R. & Bolton, B. (1993) The effect of forest disturbance on the leaf litter ant fauna in Ghana. Biodiversity & Conservation. 2 (6). p656-666.
Bergmeier, E. & Roellig, M. (2014) Diversity, threats, and conservation of European wood-pastures. In Hartel, T. & Plieninger, T. (eds.) European wood-pastures in transition: A social-ecological approach. UK: Earthscan.
Brühl, C., Eltz, T., & Linsenmair, K. (2003) Size does matter–effects of tropical rainforest fragmentation on the leaf litter ant community in Sabah, Malaysia. Biodiversity & Conservation. 12 (7). p1371-1389.
Buddle, C. (2001) Spiders (Araneae) associated with downed woody material in a deciduous forest in central Alberta, Canada. Agricultural and Forest Entomology. 3 (4). p241-251.
Buddle, C. & Shorthouse, D. (2008) Effects of experimental harvesting on spider (Araneae) assemblages in boreal deciduous forests. The Canadian Entomologist. 140 (4). p437-452.
Carpaneto, G., Mazziotta, A., Coletti, G., Luiselli, L., & Audisio, P. (2010) Conflict between insect conservation and public safety: the case study of a saproxylic beetle (Osmoderma eremita) in urban parks. Journal of Insect Conservation. 14 (5). p555-565.
Carvalho, K. & Vasconcelos, H. (1999) Forest fragmentation in central Amazonia and its effects on litter-dwelling ants. Biological Conservation. 91 (2). p151-157.
Castro, A. & Wise, D. (2010) Influence of fallen coarse woody debris on the diversity and community structure of forest-floor spiders (Arachnida: Araneae). Forest Ecology and Management. 260 (12). p2088-2101.
Dick, C., Etchelecu, G., & Austerlitz, F. (2003) Pollen dispersal of tropical trees (Dinizia excelsa: Fabaceae) by native insects and African honeybees in pristine and fragmented Amazonian rainforest. Molecular Ecology. 12 (3). p753-764.
Donovan, S., Griffiths, G., Homathevi, R., & Winder, L. (2007) The spatial pattern of soil‐dwelling termites in primary and logged forest in Sabah, Malaysia. Ecological Entomology. 32 (1). p1-10.
Eggleton, P., Bignell, D., Sands, W., Waite, B., Wood, T., & Lawton, J. (1995) The species richness of termites (Isoptera) under differing levels of forest disturbance in the Mbalmayo Forest Reserve, southern Cameroon. Journal of Tropical Ecology. 11 (1). p85-98.
Esenther, G. & Beal, R. (1979) Termite control: decayed wood bait. Sociobiology. 4 (2). p215-222.
Falk, S. (2014) Wood-pastures as reservoirs for invertebrates. In Hartel, T. & Plieninger, T. (eds.) European wood-pastures in transition: A social-ecological approach. UK: Earthscan.
Fashing, N. (1998) Functional morphology as an aid in determining trophic behaviour: the placement of astigmatic mites in food webs of water-filled tree-hole communities. Experimental & Applied Acarology. 22 (8). p435-453.
Fayle, T., Turner, E., Snaddon, J., Chey, V., Chung, A., Eggleton, P., & Foster, W. (2010) Oil palm expansion into rain forest greatly reduces ant biodiversity in canopy, epiphytes and leaf-litter. Basic and Applied Ecology. 11 (4). p337-345.
Gibb, H., Pettersson, R., Hjältén, J., Hilszczański, J., Ball, J., Johansson, T., Atlegrim, O., & Danell, K. (2006) Conservation-oriented forestry and early successional saproxylic beetles: responses of functional groups to manipulated dead wood substrates. Biological Conservation. 129 (4). p437-450.
Grove, S. (2002) Saproxylic insect ecology and the sustainable management of forests. Annual Review of Ecology and Systematics. 33 (1). p1-23.
Haila, Y. & Niemelä, J. (1999) Leaf litter and the small‐scale distribution of carabid beetles (Coleoptera, Carabidae) in the boreal forest. Ecography. 22 (4). p424-435.
Harding, P. & Rose, F. (1986) Pasture-Woodlands in Lowland Britain: A review of their importance for wildlife conservation. UK: NERC.
Herrick, O. & Gansner, D. (1987) Gypsy moth on a new frontier: forest tree defoliation and mortality. Northern Journal of Applied Forestry. 4 (3). p128-133.
Holl, K. (1995) Nectar resources and their influence on butterfly communities on reclaimed coal surface mines. Restoration Ecology. 3 (2). p76-85.
Jones, D., Susilo, F., Bignell, D., Hardiwinoto, S., Gillison, A., & Eggleton, P. (2003) Termite assemblage collapse along a land‐use intensification gradient in lowland central Sumatra, Indonesia. Journal of Applied Ecology. 40 (2). p380-391.
Jonsell, M. (2012) Old park trees as habitat for saproxylic beetle species. Biodiversity and Conservation. 21 (3). p619-642.
Jonsell, M. & Nordlander, G. (2004) Host selection patterns in insects breeding in bracket fungi. Ecological Entomology. 29 (6), p697-705.
Johnston, J. & Crossley, D. (1993) The significance of coarse woody debris for the diversity of soil mites. In McMinn, J. & Crossley, D. (eds.) Proceedings of the Workshop on Coarse Woody Debris in Southern Forests: Effects on Biodiversity. General Technical Report SE-94.
Jørgensen, D. & Quelch, P. (2014) The origins and history of medieval wood-pastures. In Hartel, T. & Plieninger, T. (eds.) European wood-pastures in transition: A social-ecological approach. UK: Earthscan.
Karban, R. (2015) Plant Sensing & Communication. USA: University of Chicago Press.
Kay, Q., Lack, A., Bamber, F., & Davies, C. (1984) Differences between sexes in floral morphology, nectar production and insect visits in a dioecious species, Silene dioica. New Phytologist. 98 (3). p515-529.
Kitahara, M., Yumoto, M., & Kobayashi, T. (2008) Relationship of butterfly diversity with nectar plant species richness in and around the Aokigahara primary woodland of Mount Fuji, central Japan. Biodiversity and Conservation. 17 (11). p2713-2734.
Koch, J., Grigg, A., Gordon, R., & Majer, J. (2010) Arthropods in coarse woody debris in jarrah forest and rehabilitated bauxite mines in Western Australia. Annals of Forest Science. 67 (1). p106-115.
Komonen, A. (2003) Distribution and abundance of insect fungivores in the fruiting bodies of Fomitopsis pinicola. Annales Zoologici Fennici. 40 (6). p495-504.
Komonen, A., Penttilä, R., Lindgren, M., & Hanski, I. (2000) Forest fragmentation truncates a food chain based on an old-growth forest bracket fungus. Oikos. 90 (1). p119-126.
Leather, S. & Bland, K. (1999) Naturalists’ Handbook 27: Insects on cherry trees. UK: The Richmond Publishing Co. Ltd.
Magura, T. (2002) Carabids and forest edge: spatial pattern and edge effect. Forest Ecology and Management. 157 (1). p23-37.
Molnár, T., Magura, T., Tóthmérész, B., & Elek, Z. (2001) Ground beetles (Carabidae) and edge effect in oak-hornbeam forest and grassland transects. European Journal of Soil Biology. 37 (4). p297-300.
Morales-Ramos, J. & Rojas, M. (2001) Nutritional Ecology of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) – Feeding Response to Commercial Wood Species. Journal of Economic Entomology. 94 (2). p516-523.
Mori, S., Itoh, A., Nanami, S., Tan, S., Chong, L., & Yamakura, T. (2014) Effect of wood density and water permeability on wood decomposition rates of 32 Bornean rainforest trees. Journal of Plant Ecology. 7 (4). p356-363.
Müller, J., Noss, R., Bussler, H., & Brandl, R. (2010) Learning from a “benign neglect strategy” in a national park: Response of saproxylic beetles to dead wood accumulation. Biological Conservation. 143 (11). p2559-2569.
Norton, R. (1980) Observations on phoresy by oribatid mites (Acari: Oribatei). International Journal of Acarology. 6 (2). p121-130.
Niemelä, J., Koivula, M., & Kotze, D. (2007) The effects of forestry on carabid beetles (Coleoptera: Carabidae) in boreal forests. Journal of Insect Conservation. 11 (1). p5-18.
Owen, D. (1978) The effect of a consumer, Phytomyza ilicis, on seasonal leaf-fall in the holly, Ilex aquifolium. Oikos. 31 (2). p268-271.
Pearce, J., Venier, L., Eccles, G., Pedlar, J., & McKenney, D. (2004) Influence of habitat and microhabitat on epigeal spider (Araneae) assemblages in four stand types. Biodiversity & Conservation. 13 (7). p1305-1334.
Ramírez-Hernández, A., Micó, E., de los Ángeles Marcos-García, M., Brustel, H., & Galante, E. (2014) The “dehesa”, a key ecosystem in maintaining the diversity of Mediterranean saproxylic insects (Coleoptera and Diptera: Syrphidae). Biodiversity and Conservation. 23 (8). p2069-2086.
Rasmont, P., Regali, A., Ings, T., Lognay, G., Baudart, E., Marlier, M., Delcarte, E., Viville, P., Marot, C., Falmagne, P., & Verhaeghe, J. (2005) Analysis of pollen and nectar of Arbutus unedo as a food source for Bombus terrestris (Hymenoptera: Apidae). Journal of Economic Entomology. 98 (3). p656-663.
Schiegg, K. (2000) Are there saproxylic beetle species characteristic of high dead wood connectivity?. Ecography. 23 (5). p579-587.
Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates.
Siitonen, J. & Ranius, T. (2015) The Importance of Veteran Trees for Saproxylic Insects. In Kirby, K. & Watkins, C. (eds.) Europe’s Changing Woods and Forests: From Wildwood to Managed Landscapes. UK: CABI.
Stokland, J., Siitonen, J., & Jonsson, B. (2012) Biodiversity in Dead Wood. UK: Cambridge University Press.
Thalmann, C., Freise, J., Heitland, W., & Bacher, S. (2003) Effects of defoliation by horse chestnut leafminer (Cameraria ohridella) on reproduction in Aesculus hippocastanum. Trees. 17 (5). p383-388.
Varady-Szabo, H. & Buddle, C. (2006) On the relationships between ground-dwelling spider (Araneae) assemblages and dead wood in a northern sugar maple forest. Biodiversity & Conservation. 15 (13). p4119-4141.
Vasconcelos, H., Pacheco, R., Silva, R., Vasconcelos, P., Lopes, C., Costa, A., & Bruna, E. (2009) Dynamics of the leaf-litter arthropod fauna following fire in a neotropical woodland savanna. PLoS One. 4 (11). p1-9.
Vasconcelos, H., Vilhena, J., & Caliri, G. (2000) Responses of ants to selective logging of a central Amazonian forest. Journal of Applied Ecology. 37 (3). p508-514.
Woodcock, P., Edwards, D., Fayle, T., Newton, R., Khen, C., Bottrell, S., & Hamer, K. (2011) The conservation value of South East Asia’s highly degraded forests: evidence from leaf-litter ants. Philosophical Transactions of the Royal Society of London B: Biological Sciences. 366 (1582). p3256-3264.