Literature about the fisher (Martes pennanti) contains the folLes rtftrences faites au ptkan (Martes pennanti) soultvent lowing contradictions: (1) the species is an old-growth specialdeux contradictions: (1) l'esptce est un s#cialiste des vieilles ist versus a forest generalist, and (2) it lives with marten (M. a m rfor& par opposition B un g6ntraliste de toutes les forCts, et (2) il icana) with minimal interaction versus densities of the two vit avec un minimum d'interaction avec la martre (M. americana) species are inversely related. These contradictions beg the quespar rapport B la densit6 inversement relite des deux esptces. Ces contradictions posent les questions suivantes B savoir quel est tions of what is fisher habitat and does habitat affect the interactions l,habitat du ptkan et comment celui-ci affecte les interactions des the Martes. These questions were examinedb~ dew Martes. Ces questions ant kt6 6mdites en fonction de l'andyse the distributions of fishers (n = 15,549) and martens (n = 40,516) de la distributions des ptkans (n = 15 549) et des martres (n = 40 harvested in Maine, 1980Maine, -1987 fr6quentes (Xmensuel = 6.5) et un couvert neigeux abondant (X total were rare in northwestern Maine but were common throughout mensue1 2 48 cm) entre les mois de decembre et mars. Les p6kans the rest of the state where snowfalls were less freq~ent. We &lent rares dms le nord-ouest du Maine mais c o m u n s dans le hypothesize that regular accumulations of deep snow reduce reste de l'6tat oii les prkipitations de neige 6taient moins fr6quentes. the fisher's fitness (via decreasing recruitment, survival, or both), Nous posons comme hypothk que l'accumukdon r6gulik de neige resulting in a low abundance in northwestern Maine. In addition, r6duit l'extension de l'aire du ptkm (au niveau de sa reproduction, we hypothesize that mns are rare in southem ~~i~~ due to de sa survie ou de ces deux 616ments), ayant pour cons6quence un petition from a dense fisher population. nese hypotheses were faible niveau de population dans le nord-ouest du Maine. De plus, nous posons cornme hypothtse que la marire est peu abondante dans evaluated looking at patterns in age and recruitment ratios of le sud du Maine par suite de la comp&tition exercte la populafishers (n = 2,706) and martens (n = 5,572) harvested in core and tion plus 61evk de gh. ces hypothtses 6 e evduks par ~6 u d e noncore habitats for 1980-1984. We found low de la distributions des 8ges et des ratios de jeunes animaux chez les of fisher recruitment (P < 0.001) in the marten's core habitat conp6kans (n = 2 706) et les martres (n = 5 572) pitgts dans le habisistent with the hypothesis that deep and frequent snowfalls tats principaux et secondaires des deux exptces entre 1980 et limit fishers. Few adult martens were harvested (P < 0.001) in the 1984. Nous avons relevt des indices faibles de reproduction (P < core habitats of fisher, consistent with our hypothesis that high 0.001) au coeur de l'habitat de la martre ce qui est consistant avec fisher densities limit ...

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2004: C a n a d a ly n x L y n x canadensis h ab ita t a n d fo re st s u c ce ssio n in n o rth ern M a in e, U S A . -W ild l. B io l. 10: 2 8 5 -2 9 4 . T h e co n tig u o u s U n ite d S tates p o p u latio n o f C a n ad a lynx L y n x canadensis w as listed as th rea ten e d in 2 00 0 . T h e lo n g -te rm v iab ility o f ly n x p o p u la tio n s a t th e so u th e rn ed g e o f th e ir g e o g ra p h ic ran g e h as b ee n h y p o th e siz e d to b e d e p e n d en t on old g row th forests; h o w ev er, lynx are a specialist p red ato r on sn o w sh o e h are L ep u s am ericanus, a species associated w ith early -su ccessio n al forests. T o q u an tify th e effec ts o f su c ce ssio n an d fo re st m a n a g e m e n t o n lan d sca p e-sca le (100 k m 2) patterns o f h ab itat o ccupancy by lynx, w e co m p ared landscape attrib utes in n o rth ern M ain e, U S A , w h ere ly n x h ad b een d etected o n snow track su r v ey s to la n d sc a p e attrib u te s w h ere su rv e y s h a d b e e n c o n d u c te d , b u t ly n x trac k s h ad n o t b ee n d etec ted . M o d e ls w ere c o n stru c te d a priori an d c o m p ared using logistic regression and A k aik e's Inform ation C riterion (A IC ), w hich q u an titativ ely b alan c es d a ta fit a n d p arsim o n y . In th e m o d e ls w ith th e lo w est (i.e. b est) A IC , ly n x w ere m o re lik e ly to o c c u r in la n d sca p es w ith m u ch re g e n e r atin g fo rest, an d less lik e ly to o cc u r in la n d sca p es w ith m u c h re c e n t clearcu t, p artial h a rv e st an d fo re ste d w etlan d . L y n x w e re n o t asso cia te d p o sitiv ely o r negatively w ith m atu re coniferous forest. A probabilistic m ap o f the m odel in di ca te d a p atc h y d istrib u tio n o f ly n x h a b ita t in n o rth e rn M ain e. A cc o rd in g to an ad d itio n a l su rv ey o f th e stu d y are a fo r ly n x trac k s d u rin g th e w in te r o f 2 0 0 3 , th e m odel correctly classified 63.5% o f th e lynx occurrences and absences. Lynx w ere m o re clo sely asso cia te d w ith y o u n g fo re sts th an m a tu re fo rests; h o w e v er, o ld -g ro w th fo re sts w e re fu n c tio n a lly a b se n t fro m th e la n d sca p e. L y n x h ab itat co u ld b e red u c ed in n o rth ern M a in e, g iv e n rec en t tren d s in fo rest m a n ag e m e n t p ractices. H arv est strateg ies h av e sh ifte d fro m c lea rc u ttin g to p artial h arv e stin g . I f th is tre n d co n tin u es, fu tu re la n d sc a p e s w ill sh ift aw ay fro m e x te n siv e re g e n e ra tin g fo re sts an d to w a rd la n d sc a p e s d o m in a te d b y p o le sized and larger stands. B ecause M aine presently supports the only verified popu la tions o f this fed erally th reaten ed species in th e eastern U n ited S tates, changes in fo re st m a n a g e m e n t p rac tice s co u ld affe c t rec o v ery e ffo rts th ro u g h o u t th at reg io n .

Spatial autocorrelation in species’ distributions has been recognized as inflating the probability of a type I error in hypotheses tests, causing biases in variable selection, and violating the assumption of independence of error terms in models such as correlation or regression. However, it remains unclear whether these problems occur at all spatial resolutions and extents, and under which conditions spatially explicit modeling techniques are superior. Our goal was to determine whether spatial models were superior at large extents and across many different species. In addition, we investigated the importance of purely spatial effects in distribution patterns relative to the variation that could be explained through environmental conditions. We studied distribution patterns of 108 bird species in the conterminous United States using ten years of data from the Breeding Bird Survey. We compared the performance of spatially explicit regression models with non‐spatial regression models using Akaike's information criterion. In addition, we partitioned the variance in species distributions into an environmental, a pure spatial and a shared component. The spatially‐explicit conditional autoregressive regression models strongly outperformed the ordinary least squares regression models. In addition, partialling out the spatial component underlying the species’ distributions showed that an average of 17% of the explained variation could be attributed to purely spatial effects independent of the spatial autocorrelation induced by the underlying environmental variables. We concluded that location in the range and neighborhood play an important role in the distribution of species. Spatially explicit models are expected to yield better predictions especially for mobile species such as birds, even in coarse‐grained models with a large extent.

Aim To explore biogeographic patterns of terrestrial vertebrates in Maine, USA using techniques that would describe local and spatial correlations with the environment. Location Maine, USA. Methods We delineated the ranges within Maine (86,156 km2) of 275 species using literature and expert review. Ranges were combined into species richness maps, and compared to geomorphology, climate, and woody plant distributions. Methods were adapted that compared richness of all vertebrate classes to each environmental correlate, rather than assessing a single explanatory theory. We partitioned variation in species richness into components using tree and multiple linear regression. Methods were used that allowed for useful comparisons between tree and linear regression results. For both methods we partitioned variation into broad‐scale (spatially autocorrelated) and fine‐scale (spatially uncorrelated) explained and unexplained components. By partitioning variance, and using both tree and linear regression in analyses, we explored the degree of variation in species richness for each vertebrate group that could be explained by the relative contribution of each environmental variable. Results In tree regression, climate variation explained richness better (92% of mean deviance explained for all species) than woody plant variation (87%) and geomorphology (86%). Reptiles were highly correlated with environmental variation (93%), followed by mammals, amphibians, and birds (each with 84–82% deviance explained). In multiple linear regression, climate was most closely associated with total vertebrate richness (78%), followed by woody plants (67%) and geomorphology (56%). Again, reptiles were closely correlated with the environment (95%), followed by mammals (73%), amphibians (63%) and birds (57%). Main conclusions Comparing variation explained using tree and multiple linear regression quantified the importance of nonlinear relationships and local interactions between species richness and environmental variation, identifying the importance of linear relationships between reptiles and the environment, and nonlinear relationships between birds and woody plants, for example. Conservation planners should capture climatic variation in broad‐scale designs; temperatures may shift during climate change, but the underlying correlations between the environment and species richness will presumably remain.