Topographic representation of vocal frequency demonstrated by microstimulation of anterior cingulate cortex in the echolocating bat,Pteronotus parnelli parnelli

1. A midline region of brain dorsal and anterior to the corpus callosum, presumably anterior cingulate cortex, has been explored for its role in the production of vocalization in the mustached bat, Pteronotus p. parnelli. 2. Vocalizations elicited by microstimulation were virtually indistinguishable from natural biosonar sounds. The spectral content, relative intensity of harmonic components, and durations of emitted pulses are comparable to spontaneous emissions. 3. The frequencies of elicited vocalizations were within the range typically used by the mustached bat during Doppler-shift compensation. The frequency of the second-harmonic constant-frequency component (CF2) covered the range from 57-62 kHz, but was most commonly emitted at frequencies of 59-61 kHz. 4. An increase in the frequency of vocalizations over a number of consecutive pulses towards a steady-state plateau is evident in both spontaneous vocalizations and emissions elicited by microstimulation just above threshold. Increasing the stimulus intensity caused the frequency of emissions to approach the steady state more rapidly. 5. The anterior cingulate cortex appears to be organized topographically for increasing frequency of elicited biosonar sounds along a rostrocaudal axis. The area from which biosonar emissions were elicited was overrepresented for a 2 kHz band of frequencies just below the bats' CF2 resting frequency. Audible vocalizations with a complex spectrum resembling social cries can also be elicited by microstimulation, but only in an area that is adjacent and posterior to the biosonar region. 6. Some examples of both elicited and spontaneous vocalizations contained a relative intensity pattern of the harmonic components which deviated from the typical pattern. This suggests that mustached bats are capable of actively altering the spectrum of their pulses to subserve different tasks in echolocation.     

Biosonar-inspired technology: goals, challenges and insights

Bioinspired engineering based on biosonar systems in nature is reviewed and discussed in terms of the merits of different approaches and their results: biosonar systems are attractive technological paragons because of their capabilities, built-in task-specific knowledge, intelligent system integration and diversity. Insights from the diverse set of sensing tasks solved by bats are relevant to a wide range of application areas such as sonar, biomedical ultrasound, non-destructive testing, sensors for autonomous systems and wireless communication. Challenges in the design of bioinspired sonar systems are posed by transducer performance, actuation for sensor mobility, design, actuation and integration of beamforming baffle shapes, echo encoding for signal processing, estimation algorithms and their implementations, as well as system integration and feedback control. The discussed examples of experimental systems have capabilities that include localization and tracking using binaural and multiple-band hearing as well as self-generated dynamic cues, classification of small deterministic and large random targets, beamforming with bioinspired baffle shapes, neuromorphic spike processing, artifact rejection in sonar maps and passing range estimation. In future research, bioinspired engineering could capitalize on some of its strengths to serve as a model system for basic automation methodologies for the bioinspired engineering process.     

MORPHOLOGICAL EVOLUTION IN MUROID RODENTS I. CONSERVATIVE PATTERNS OF CRANIOMETRIC COVARIANCE AND THEIR ONTOGENETIC BASIS IN THE NEOTROPICAL GENUS ZYGODONTOMYS

Analyses of craniodental measurement data from 15 wild-collected population samples of the Neotropical muroid rodent genus Zygodontomys reveal consistent patterns of relative variability and correlation that suggest a common latent structure. Eigenanalysis of each sample covariance matrix of logarithms yields a first principal component that accounts for a large fraction of the total variance. Variances of subsequent sample principal components are much smaller, and the results of bootstrap resampling together with asymptotic statistics suggest that characteristic roots of the covariance matrix after the first are seldom distinct. The coefficients of normalized first principal components are strikingly similar from sample to sample: inner products of these vectors reveal an average between-sample correlation of 0.989, and the mean angle of divergence is only about eight degrees. Since first principal component coefficients identify the same contrasts among variables as comparisons of relative variability and correlation, we conclude that a single factor accounts for most of the common latent determination of these sample dispersions. Analyses of variance based on toothwear (a coarse index of age) and sex in the wild-collected samples, and on known age and sex in a captive-bred population, reveal that specimen scores on sample first principal components are age- and sex-dependent; residual sample dispersion, however, is essentially unaffected by age, sex, or age × sex interaction. The sample first principal component therefore reflects the covariance among measured dimensions induced by general growth, and its coefficients are interpretable as exponents of postnatal growth allometry. Path-analytic models that incorporate prior knowledge of the equivalent allometric effects of general growth within these samples can be used to decompose the between-sample variance by factors corresponding to other ontogenetic mechanisms of form change. The genetic or environmental determinants of differences in sample mean phenotypes induced by such mechanisms, however, can be demonstrated only by experiment.     

Noseleaf dynamics during pulse emission in horseshoe bats

Horseshoe bats emit their biosonar pulses nasally and diffract the outgoing ultrasonic waves by conspicuous structures that surrounded the nostrils. Here, we report quantitative experimental data on the motion of a prominent component of these structures, the anterior leaf, using synchronized laser Doppler vibrometry and acoustic recordings in the greater horseshoe bat (Rhinolophus ferrumequinum). The vibrometry data has demonstrated non-random motion patterns in the anterior leaf. In these patterns, the outer rim of the walls of the anterior leaf twitches forward and inwards to decrease the aperture of the noseleaf and increase the curvature of its surfaces. Noseleaf displacements were correlated with the emitted ultrasonic pulses. After their onset, the inward displacements increased monotonically towards their maximum value which was always reached within the duration of the biosonar pulse, typically towards its end. In other words, the anterior leaf's surfaces were moving inwards during most of the pulse. Non-random motions were not present in all recorded pulse trains, but could apparently be switched on or off. Such switches happened between sequences of consecutive pulses but were never observed between individual pulses within a sequence. The amplitudes of the emitted biosonar pulse and accompanying noseleaf movement were not correlated in the analyzed data set. The measured velocities of the noseleaf surface were too small to induce Doppler shifts of a magnitude with a likely significance. However, the displacement amplitudes were significant in comparison with the overall size of the anterior leaf and the sound wavelengths. These results indicate the possibility that horseshoe bats use dynamic sensing principles on the emission side of their biosonar system. Given the already available evidence that such mechanisms exist for biosonar reception, it may be hypothesized that time-variant mechanisms play a pervasive role in the biosonar sensing of horseshoe bats.     

A morphometric study on morphological plasticity of shell form in crevice-dwelling Pterioida (Bivalvia)

Relative warp analysis and eigenshape analysis were used to explore the patterns of variation of erratic shell shapes in and among six species of crevice-dwelling pterioid bivalves. The results of morphometric analyses revealed that a great deal of the variance of shell shape within each species can be reduced into principal components which display patterns of variation common to all species examined. In the species with striking variability, a few sets of principal components account for most of the variance of shell shape. On the other hand, in the species lacking considerable variability, several components contribute to form a given variety. Comparison of relative warp and eigenshape scores with centroid sizes indicates that the direction of ontogenetic shape change has been modified through evolution to produce adaptations to habitats such as crevices or the undersides of rocks.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79, 285–297.     

Labile cochlear tuning in the mustached bat

Summary Acoustic stimuli near 60 kHz elicit pronounced resonance in the cochlea of the mustached bat (Pteronotus parnellii parnellii). The cochlear resonance frequency (CRF) is near the second harmonic, constant frequency (CF2) component of the bat's biosonar signals. Within narrow bands where CF2 and third harmonic (CF3) echoes are maintained, the cochlea has sharp tuning characteristics that are conserved throughout the central auditory system. The purpose of this study was to examine the effects of temperature-related shifts in the CRF on the tuning properties of neurons in the cochlear nucleus and inferior colliculus.Eighty-two single and multi-unit recordings were characterizedin 6 awake bats with chronically implanted cochlear microphonic electrodes. As the CRF changed with body temperature, the tuning curves of neurons sharply tuned to frequencies near the CF2 and CF3 shifted with the CRF in every case, yielding a change in the unit's best frequency. The results show that cochlear tuning is labile in the mustached bat, and that this lability produces tonotopic shifts in the frequency response of central auditory neurons. Furthermore, results provide evidence of shifts in the frequency-to-place code within the sharply tuned CF2 and CF3 regions of the cochlea. In conjunction with the finding that biosonar emission frequency and the CRF shift concomitantly with temperature and flight, it is concluded that the adjustment of biosonar signals accommodates the shifts in cochlear and neural tuning that occur with active echolocation.Abbreviations BF best frequency - CF characteristic frequency - CF2, CF3 second and third harmonic, constant frequency components of the biosonar signal - CM cochlear microphonic - CN cochlear nucleus - CRF cochlear resonance frequency - IC inferior colliculus - MT minimum threshold - OAE otoacoustic emission - Q_10dB BF (or CF) divided by the response bandwidth at 10 dB above MT     

Geometrical principal component analysis of planar-segments of the three-channel lissajous' trajectory of human auditory brain stem evoked potentials

Three-Channel Lissajous' Trajectories (3CLTs) of Auditory Brain Stem Evoked Potentials (ABEP) were obtained from 15 normal humans. Planar-segments of 3CLT were identified and the orientations of the first two geometrical principal components, which interact to produce the planar-segments, were calculated. Each principal component's orientation in voltage space was quantified by its coefficients (A, B and C). Intersubject variability of these orientations was comparable to the variability of plane orientations. The principal components of planar-segments can indicate the type of generator activity that is involved in the formation of planar-segments. The results of this analysis indicate that planarity of each 3CLT component is produced by the interaction of simultaneous multiple generators, or by a single synchronous generator which changes its orientation. The coefficients of these principal components may complement plane coefficients as quantitative indices of 3CLT of ABEP.     

Click-based echolocation in bats: not so primitive after all

Echolocating bats of the genus Rousettus produce click sonar signals, using their tongue (lingual echolocation). These signals are often considered rudimentary and are believed to enable only crude performance. However, the main argument supporting this belief, namely the click’s reported long duration, was recently shown to be an artifact. In fact, the sonar clicks of Rousettus bats are extremely short, ~50–100 μs, similar to dolphin vocalizations. Here, we present a comparison between the sonar systems of the ‘model species’ of laryngeal echolocation, the big brown bat (Eptesicus fuscus), and that of lingual echolocation, the Egyptian fruit bat (Rousettus aegyptiacus). We show experimentally that in tasks, such as accurate landing or detection of medium-sized objects, click-based echolocation enables performance similar to laryngeal echolocators. Further, we describe a sophisticated behavioral strategy for biosonar beam steering in clicking bats. Finally, theoretical analyses of the signal design—focusing on their autocorrelations and wideband ambiguity functions—predict that in some aspects, such as target ranging and Doppler-tolerance, click-based echolocation might outperform laryngeal echolocation. Therefore, we suggest that click-based echolocation in bats should be regarded as a viable echolocation strategy, which is in fact similar to the biosonar used by most echolocating animals, including whales and dolphins.     

Principles and methods of geometric morphometrics

The basic concepts, notions and methods of geometric morphometrics (GM) are considered. This approach implies multivariate analysis of landmark coordinates located following certain rules on the surface of a morphological object. The aim of GM is to reveal differences between morphological objects by their shapes as such, the "size factor" being excluded. The GM is based on the concept of Kendall's space (KS) defined as a hypersphere with points distributed on its surface. These points are the shapes defined as aligned landmark configurations. KS is a non-Euclidian space, its metrics called Procrustes is defined by landmark configuration of a reference shape relative to which other shapes are aligned and compared. The differences among shapes are measured as Procrustes distances between respective points. For the linear methods of multivariate statistics to be applied to comparison of shapes, the respective points are projected onto the tangent plane (tangent space), the tangent point being defined by the reference. There are two principal methods of shape comparisons in GM: the Procrustes superimposition (a version of the least squares analysis) and thin-plate spline analysis. In the first case, Procrustes residuals are the outcome shape variables which remain after isometric alignment of the shapes being compared. Their summation over all landmarks yields Procrustes distances among these shapes. The Procrustes distances can be used in multivariate analyses just as the Euclidian distances. In the second case, the shapes are fitted to the references by stretching/compressing and shearing until complete identity of their landmark configurations. Eigenvectors of resulting bending energy matrix are defined as new shape variables, principal warps which yield another shape space with the origin defined by the reference. Projections of the shapes being compared onto principal warps yield partial warps, and their covariance matrix decomposition into eigenvectors yields relative warps which are similar to principal components (in particular, they are mutually orthogonal). Both partial and relative warps can be used in many multivariate statistic analyses as quantitative shape variables. Results of thin-plate spline analysis can be represented graphically by transformation grid which displays type, amount and localization of the shape differences. Basis rules of sample composition and landmark positioning to be used in GM are considered. At present, rigid (with minimal degrees of freedom) 2D morphological objects are most suitable for GM applications. It is important to recognize three type of real landmarks, and additionally semi-landmarks and "virtual" landmarks. Some procedures of thin-plate spline analysis are considered exemplified by some study cases, as well as applications of some standard multivariate methods to GM results. They make it possible to evaluate correlation between different shapes, as well as between a shape and some non-shape variables (linear measurements etc); to evaluate the differences among organisms by shape of a morphological structure; to identify landmarks which most accounted for both correlation and differences between the shapes. An annotated list of most popular softwares for GM is provided.     

Lancet Dynamics in Greater Horseshoe Bats,Rhinolophus ferrumequinum

Echolocating greater horseshoe bats (Rhinolophus ferrumequinum) emit their biosonar pulses nasally, through nostrils surrounded by fleshy appendages (‘noseleaves’) that diffract the outgoing ultrasonic waves. Movements of one noseleaf part, the lancet, were measured in live bats using two synchronized high speed video cameras with 3D stereo reconstruction, and synchronized with pulse emissions recorded by an ultrasonic microphone. During individual broadcasts, the lancet briefly flicks forward (flexion) and is then restored to its original position. This forward motion lasts tens of milliseconds and increases the curvature of the affected noseleaf surfaces. Approximately 90% of the maximum displacements occurred within the duration of individual pulses, with 70% occurring towards the end. Similar lancet motions were not observed between individual pulses in a sequence of broadcasts. Velocities of the lancet motion were too small to induce Doppler shifts of a biologically-meaningful magnitude, but the maximum displacements were significant in comparison with the overall size of the lancet and the ultrasonic wavelengths. Three finite element models were made from micro-CT scans of the noseleaf post mortem to investigate the acoustic effects of lancet displacement. The broadcast beam shapes were found to be altered substantially by the observed small lancet movements. These findings demonstrate that—in addition to the previously described motions of the anterior leaf and the pinna—horseshoe bat biosonar has a third degree of freedom for fast changes that can happen on the time scale of the emitted pulses or the returning echoes and could provide a dynamic mechanism for the encoding of sensory information.     

Frequency tuning, latencies, and responses to frequency-modulated sweeps in the inferior colliculus of the echolocating bat, Eptesicus fuscus

Neurons in the inferior colliculus (IC) of the awake big brown bat, Eptesicus fuscus, were examined for joint frequency and latency response properties which could register the timing of the bat's frequency-modulated (FM) biosonar echoes. Best frequencies (BFs) range from 10 kHz to 100 kHz with 50% tuning widths mostly from 1 kHz to 8 kHz. Neurons respond with one discharge per 2-ms tone burst or FM stimulus at a characteristic latency in the range of 3–45 ms, with latency variability (SD) of 50 μs to 4–6 ms or more. BF distribution is related to biosonar signal structure. As observed previously, on a linear frequency scale BFs appear biased to lower frequencies, with 20–40 kHz overrepresented. However, on a hyperbolic frequency (linear period) scale BFs appear more uniformly distributed, with little overrepresentation. The cumulative proportion of BFs in FM₁ and FM₂ bands reconstructs a scaled version of the spectrogram of FM broadcasts. Correcting FM latencies for absolute BF latencies and BF time-in-sweep reveals a subset of IC cells which respond dynamically to the timing of their BFs in FM sweeps. Behaviorally, Eptesicus perceives echo delay and phase with microsecond or even submicrosecond accuracy and resolution, but even with use of phase-locked FM and tone-burst stimuli the cell-by-cell precision of IC time-frequency registration seems inadequate by itself to account for the temporal acuity exhibited by the bat. Accepted: 21 June 1997     

Encephalization and quantitative brain composition in bats in relation to their life-habits

A quantitative analysis of the brains of 43 bat species is presented. Eleven brain components were studied. The species were arranged according to seven distinct dietary groups and it was found that the relative development of the principal components is related to those groups. The importance of neocorticalization as a reflection of evolution of all the bats in contrast to specialization in some species is stressed. This work gives a clearer view of Chiropteran progressiveness or primitiveness: the insectivorous forms occupy the least advanced, although most specialized, level; the vampires, the carnivorous species and the flying foxes are at the top of the scale. The importance of behaviour and the relative development of the central nervous system in the hierarchial classification of mammals is stressed.     

"Synthetic" maps of the Mari gene pool (from immunobiochemical polymorphism data)]

Models of geographic distribution of 33 alleles of 10 loci (AB0, TF, GC, PI, HP, AHS, F13B, ACP1, PGM1, GLO1) in the indigenous population of five raions (districts) of Marii El Republic were analyzed by cartographic statistical methods. Based on 33 maps for individual alleles, synthetic maps were constructed; they reflected the general characteristics of the spatial variability of the Mari gene pool. A map of reliability of the synthetic maps was also obtained. This study was the first to use estimates of the reliability of the gene-geographic prognosis for constructing and interpreting the maps of principal components. Synthetic maps of principal components reveal the geography of the main factors that determine the genetic diversity of the Maris. In the map of the first principal component (accounting for 25.5% of the total variation of the Mari gene pool), isolines clearly ran in the latitudinal direction; i.e., the variability exhibited a north-south gradient. The direction of changes reflects the characteristic features of the microevolution of the Mari gene pool, because it differs from the direction of the principal components of in the total Ural gene pool. The second principal component (24.3% of variation) also exhibited a latitudinal gradient in the western part of Marii El. In the eastern part of the republic, isolines drastically change their direction and display a marked west-east gradient. This longitudinal orientation of principal components is characteristic of the Maris in the synthetic maps of the Ural region. Contributions of individual genes in the variation of principal components were analyzed. In proceeding from the geographic space to the space of principal components, it was found that Highland Maris are separated from Meadow Maris not only geographically, but also genetically.     

A robust,high‐throughput method for computing maize ear,cob, and kernel attributes automatically from images

Grain yield of the maize plant depends on the sizes, shapes, and numbers of ears and the kernels they bear. An automated pipeline that can measure these components of yield from easily‐obtained digital images is needed to advance our understanding of this globally important crop. Here we present three custom algorithms designed to compute such yield components automatically from digital images acquired by a low‐cost platform. One algorithm determines the average space each kernel occupies along the cob axis using a sliding‐window Fourier transform analysis of image intensity features. A second counts individual kernels removed from ears, including those in clusters. A third measures each kernel's major and minor axis after a Bayesian analysis of contour points identifies the kernel tip. Dimensionless ear and kernel shape traits that may interrelate yield components are measured by principal components analysis of contour point sets. Increased objectivity and speed compared to typical manual methods are achieved without loss of accuracy as evidenced by high correlations with ground truth measurements and simulated data. Millimeter‐scale differences among ear, cob, and kernel traits that ranged more than 2.5‐fold across a diverse group of inbred maize lines were resolved. This system for measuring maize ear, cob, and kernel attributes is being used by multiple research groups as an automated Web service running on community high‐throughput computing and distributed data storage infrastructure. Users may create their own workflow using the source code that is staged for download on a public repository.     

Hawkmoths produce anti-bat ultrasound

Bats and moths have been engaged in aerial warfare for nearly 65 Myr. This arms race has produced a suite of counter-adaptations in moths, including bat-detecting ears. One set of defensive strategies involves the active production of sound; tiger moths'' ultrasonic replies to bat attack have been shown to startle bats, warn the predators of bad taste and jam their biosonar. Here, we report that hawkmoths in the Choerocampina produce entirely ultrasonic sounds in response to tactile stimulation and the playback of biosonar attack sequences. Males do so by grating modified scraper scales on the outer surface of the genital valves against the inner margin of the last abdominal tergum. Preliminary data indicate that females also produce ultrasound to touch and playback of echolocation attack, but they do so with an entirely different mechanism. The anti-bat function of these sounds is unknown but might include startling, cross-family acoustic mimicry, warning of unprofitability or physical defence and/or jamming of echolocation. Hawkmoths present a novel and tractable system to study both the function and evolution of anti-bat defences.     

Relationships among ontogenetic,static, and evolutionary allometry

The relationship between ontogenetic, static, and evolutionary levels of allometry is investigated. Extrapolation from relative size relationships in adults to relative growth in ontogeny depends on the variability of slopes and intercepts of ontogenetic vectors relative to variability in length of the vector. If variability in slopes and intercepts is low relative to variability in length, ontogenetic and static allometries will be similar. The similarity of ontogenetic and static allometries was tested by comparing the first principal component, or size vector, for correlations among 48 cranial traits in a cross-sectional ontogenetic sample of rhesus macaques from Cayo Santiago with a static sample from which all age- and sex-related variation had been removed. The vector correlation between the components is high but significantly less than one while two of three allometric patterns apparent in the ontogenetic component are not discernable in the static component. This indicates that there are important differences in size and shape relationships among adults and within ontogenies. Extrapolation from intra- or interspecific phenotypic allometry to evolutionary allometry is shown to depend on the similarity of genetic and phenotypic allometry patterns. Similarity of patterns was tested by comparing the first principal components of the phenotypic, genetic, and environmental correlation matrices calculated using standard quantitative genetic methods. The patterns of phenotypic, genetic, and environmental allometry are dissimilar; only the environmental allometries show ontogenetic allometric patterns. This indicates that phenotypic allometry may not be an accurate guide to patterns of evolutionary change in size and shape.     

Morphometric analysis of dinosaur eggshells: constraints of size on shape

Studies on fossil eggs and eggshells have been traditionally focused on analysis of microstructure and systematic classification, but few attempts have been made to examine the variability of eggshell characters. This work examines the variability of one diagnostic character, shape of the calcitic units, of some dinosaur eggshells by using outline shape analysis (elliptic Fourier analysis). The studied material belongs to five different oospecies of the parafamily Megaloolithidae Zhao, 1979. To test shape variation within and between oospecies, an analysis on 129 outlines was carried out and their variability was summarised by principal component analysis. We then tested if the shape of megaloolithid units changes according to size (i.e. allometry). A regression analysis between eggshell unit shape and two different size measurements (centroid size and eggshell thickness) showed that the thinnest eggshells (thickness ≤ 1 mm) have different shapes than thicker ones ( ≥ 2.5 mm). Our results stress that the variability in the shape of eggshell units in Megaloolithus oospecies is correlated to size (i.e. eggshell thickness), a phenomenon that should be then considered carefully when determining oospecies, since a single oospecies can show both a wide range of eggshell thickness and combined with different eggshell unit shapes.     

Orienting responses and vocalizations produced by microstimulation in the superior colliculus of the echolocating bat, Eptesicus fuscus

An echolocating bat actively controls the spatial acoustic information that drives its behavior by directing its head and ears and by modulating the spectro-temporal structure of its outgoing sonar emissions. The superior colliculus may function in the coordination of these orienting components of the bat's echolocation system. To test this hypothesis, chemical and electrical microstimulation experiments were carried out in the superior colliculus of the echolocating bat, Eptesicus fuscus, a species that uses frequency modulated sonar signals. Microstimulation elicited pinna and head movements, similar to those reported in other vertebrate species, and the direction of the evoked behaviors corresponded to the site of stimulation, yielding a map of orienting movements in the superior colliculus. Microstimulation of the bat superior colliculus also elicited sonar vocalizations, a motor behavior specific to the bat's acoustic orientation by echolocation. Electrical stimulation of the adjacent periaqueductal gray, shown to be involved in vocal production in other mammalian species, elicited vocal signals resembling acoustic communication calls of E. fuscus. The control of vocal signals in the bat is an integral part of its acoustic orienting system, and our findings suggest that the superior colliculus supports diverse and species-relevant sensorimotor behaviors, including those used for echolocation.     

A comparison of individual‐based genetic distance metrics for landscape genetics

A major aim of landscape genetics is to understand how landscapes resist gene flow and thereby influence population genetic structure. An empirical understanding of this process provides a wealth of information that can be used to guide conservation and management of species in fragmented landscapes and also to predict how landscape change may affect population viability. Statistical approaches to infer the true model among competing alternatives are based on the strength of the relationship between pairwise genetic distances and landscape distances among sampled individuals in a population. A variety of methods have been devised to quantify individual genetic distances, but no study has yet compared their relative performance when used for model selection in landscape genetics. In this study, we used population genetic simulations to assess the accuracy of 16 individual‐based genetic distance metrics under varying sample sizes and degree of population genetic structure. We found most metrics performed well when sample size and genetic structure was high. However, it was much more challenging to infer the true model when sample size and genetic structure was low. Under these conditions, we found genetic distance metrics based on principal components analysis were the most accurate (although several other metrics performed similarly), but only when they were derived from multiple principal components axes (the optimal number varied depending on the degree of population genetic structure). Our results provide guidance for which genetic distance metrics maximize model selection accuracy and thereby better inform conservation and management decisions based upon landscape genetic analysis.