Are we conserving peripheral populations? An analysis of range structure of longhorn beetles (Coleoptera: Cerambycidae) in Finland

Abstract

This paper characterises range structures of longhorn beetles (Coleoptera: Cerambycidae) occurring in Finland and classifies species as resource (host plant), substrate (specific host plant qualities) or climate limited. This information is then used to evaluate whether the IUCN red-list classification applied in Finland is directed towards peripheral European populations. Thirty (37%) longhorn beetle species are red-listed in Finland. Limited host plant distribution is adequate in explaining the red-list status for 43% of the red-listed species. All of these species are dependent on hardwood trees. Of the red-listed species that are dependent on widespread host plants, 30% have a limited extent of occurrence as well as a small area of occupancy in Finland. As these species are widespread outside Fennoscandia, their range in Finland is most likely limited by climate. Twenty per cent of the red-listed species have a wide extent of occurrence, albeit a small area of occupancy in Finland. As these species are dependent on widespread host plant species, but require specific substrate qualities (e.g. decaying, large diameter trunks), it is likely that their range is restricted by anthropogenic activities, mainly forestry and agriculture. The present study shows that the red-list classification in Finland is directed towards peripheral European populations. This study, however, did not address the conservation value of these populations.

Appendix

Classification of Finnish red-listed longhorn beetles (n = 30) in ecological groups based on their range size, range extent and resource use. Range size in Finland is the number of 50 km × 50 km grid cells occupied (max. 170) and in Europe the number of countries occupied (max. 26, incl. Finland; see Methods for the countries included). Range extent is the diagonal distance (rounded to the nearest integer; max. 1,390 km) between latitudinal and longitudinal extent. Host plant column gives the documented main host plants in Finland, and if not known, the most likely host plants based on observations in northern Europe. Species can occasionally use other host plants than the ones listed.

Species groups	Range size		Extent Finland	IUCN status	Host plants
	Finland	Europe
Hardwood
Rhamnusium bicolor	1	18	71	CR	Ulmus laevis
Anoplodera sexguttata	1	23	71	EN	Quercus robur
Strangalia attenuata	1	21	71	CR	Quercus robur
Phymatodes testaceus	2	24	180	EN	Quercus robur
Clytus arietis	1	21	71	VU	Quercus robur
Plagionotus arcuatus	2	23	141	CR	Quercus robur
Chlorophorus herbstii	2	14	316	EN	Tilia cordata
Mesosa myops	1	3	71	CR	Quercus robur, Tilia cordata
Oplosia cinerea	4	16	283	VU	Tilia cordata
Pogonocherus hispidus	4	24	224	VU	Tilia cordata, Ulmus laevis
Leiopus nebulosus	4	23	180	NT	Quercus robur, Corylus avellana
Exocentrus lusitanus	9	18	354	NT	Tilia cordata
Stenostola dubia	10	19	292	NT	Tilia cordata, other deciduous
Temperate
Prionus coriarius	5	25	364	NT	Pinus sylvestris
Leptura pubescens	4	19	354	EN	Pinus sylvestris
Leptura maculata	2	25	112	VU	Betula spp., other deciduous
Phytoecia cylindrica	4	23	292	VU	Anthriscus sylvestris
Stenocorus meridianus a	5	22	430	VU	Hardwoods, other deciduous
Eastern
Tetropium aquilonium	1	2	71	NT	Picea abies
Acmaeops smaragdula	4	6	474	VU	Coniferous
Nivellia sanguinosa	2	9	474	EN	Deciduous
Leptura nigripes	6	9	583	VU	Betula spp.
Leptura thoracica	1	7	71	CR	Populus tremula
Substrate limited
Tragosoma depsarium	9	16	763	VU	Pinus sylvestris
Acmaeops septentrionis	17	14	962	VU	Picea abies
Acmaeops marginata	6	16	636	VU	Pinus sylvestris
Xylotrechus rusticus	39	22	1,141	NT	Populus tremula
Monochamus urussovii	22	6	1,012	VU	Picea abies
Saperda perforata	20	16	890	NT	Populus tremula
Miscellaneous
Obrium cantharium b	27	19	763	VU	Populus tremula

1. ^a The primary host plants of the species are hardwoods, but the species must be able to use other host trees in Finland as it has been documented from locations without hardwoods.
2. ^b  Obrium cantharium is not included in the group ‘Substrate limited’ based on the information on its specific substrate requirements (e.g. branches of Populus tremula); the species may simply be difficult to find and thus artificially rare.