Environmental DNA methods for biosecurity and invasion biology in terrestrial ecosystems: Progress, pitfalls, and prospects.

Analysis of environmental DNA (eDNA) enables indirect detection of species without the need to directly observe and sample them. For biosecurity and invasion biology, eDNA-based methods are useful to address biological invasions at all phases, from detecting arrivals to confirming eradication of past invasions. We conducted a systematic review of the literature and found that in biosecurity and invasion biology, eDNA has primarily been used to detect new incursions and monitor spread in marine and freshwater ecosystems, with much slower uptake in terrestrial ecosystems, reflecting a broader trend common to the usage of eDNA tools. In terrestrial ecosystems, eDNA research has mostly focussed on the use of eDNA metabarcoding to characterise biodiversity, rather than targeting biosecurity threats or non-native populations. We discuss how eDNA-based methods are being applied to terrestrial ecosystems for biosecurity and managing non-native populations at each phase of the invasion continuum: transport, introduction, establishment, and spread; across different management options: containment, control, and eradication; and for detecting the impact of non-native organisms. Finally, we address some of the current technical issues and caveats of eDNA-based methods, particularly for terrestrial ecosystems, and how these might be solved. As eDNA-based methods improve, they will play an increasingly important role in the early detection and adaptive management of biological invasions, and the implementation of effective biosecurity controls.

An integrative bioinformatics pipeline shows that honeybee-associated microbiomes are driven primarily by pollen composition.

The microbiomes associated with bee nests influence colony health through various mechanisms, although it is not yet clear how honeybee congeners differ in microbiome assembly processes, in particular the degrees to which floral visitations and the environment contribute to different aspects of diversity. We used DNA metabarcoding to sequence bacterial 16S rRNA from honey and stored pollen from nests of 4 honeybee species (Apis cerana, A. dorsata, A. florea, and A. laboriosa) sampled throughout Yunnan, China, a global biodiversity hotspot. We developed a computational pipeline integrating multiple databases for quantifying key facets of diversity, including compositional, taxonomic, phylogenetic, and functional ones. Further, we assessed candidate drivers of observed microbiome dissimilarity, particularly differences in floral visitations, habitat disturbance, and other key environmental variables. Analyses revealed that microbiome alpha diversity was broadly equivalent across the study sites and between bee species, apart from functional diversity which was very low in nests of the reclusive A. laboriosa. Turnover in microbiome composition across Yunnan was driven predominantly by pollen composition. Human disturbance negatively impacted both compositional and phylogenetic alpha diversity of nest microbiomes, but did not correlate with microbial turnover. We herein make progress in understanding microbiome diversity associated with key pollinators in a biodiversity hotspot, and provide a model for the use of a comprehensive informatics framework in assessing pattern and drivers of diversity, which enables the inclusion of explanatory variables both subtly and fundamentally different and enables elucidation of emergent or unexpected drivers.

Plants, pollinators and their interactions under global ecological change: The role of pollen DNA metabarcoding.

Anthropogenic activities are triggering global changes in the environment, causing entire communities of plants, pollinators and their interactions to restructure, and ultimately leading to species declines. To understand the mechanisms behind community shifts and declines, as well as monitoring and managing impacts, a global effort must be made to characterize plant-pollinator communities in detail, across different habitat types, latitudes, elevations, and levels and types of disturbances. Generating data of this scale will only be feasible with rapid, high-throughput methods. Pollen DNA metabarcoding provides advantages in throughput, efficiency and taxonomic resolution over traditional methods, such as microscopic pollen identification and visual observation of plant-pollinator interactions. This makes it ideal for understanding complex ecological networks and their responses to change. Pollen DNA metabarcoding is currently being applied to assess plant-pollinator interactions, survey ecosystem change and model the spatiotemporal distribution of allergenic pollen. Where samples are available from past collections, pollen DNA metabarcoding has been used to compare contemporary and past ecosystems. New avenues of research are possible with the expansion of pollen DNA metabarcoding to intraspecific identification, analysis of DNA in ancient pollen samples, and increased use of museum and herbarium specimens. Ongoing developments in sequencing technologies can accelerate progress towards these goals. Global ecological change is happening rapidly, and we anticipate that high-throughput methods such as pollen DNA metabarcoding are critical for understanding the evolutionary and ecological processes that support biodiversity, and predicting and responding to the impacts of change.

Genomics reveals the history of a complex plant invasion and improves the management of a biological invasion from the South African-Australian biotic exchange.

Many plants exchanged in the global redistribution of species in the last 200 years, particularly between South Africa and Australia, have become threatening invasive species in their introduced range. Refining our understanding of the genetic diversity and population structure of native and alien populations, introduction pathways, propagule pressure, naturalization, and initial spread, can transform the effectiveness of management and prevention of further introductions. We used 20,221 single nucleotide polymorphisms to reconstruct the invasion of a coastal shrub, Chrysanthemoides monilifera ssp. rotundata (bitou bush) from South Africa, into eastern Australia (EAU), and Western Australia (WAU). We determined genetic diversity and population structure across the native and introduced ranges and compared hypothesized invasion scenarios using Bayesian modeling. We detected considerable genetic structure in the native range, as well as differentiation between populations in the native and introduced range. Phylogenetic analysis showed the introduced samples to be most closely related to the southern-most native populations, although Bayesian analysis inferred introduction from a ghost population. We detected strong genetic bottlenecks during the founding of both the EAU and WAU populations. It is likely that the WAU population was introduced from EAU, possibly involving an unsampled ghost population. The number of private alleles and polymorphic SNPs successively decreased from South Africa to EAU to WAU, although heterozygosity remained high. That bitou bush remains an invasion threat in EAU, despite reduced genetic diversity, provides a cautionary biosecurity message regarding the risk of introduction of potentially invasive species via shipping routes.

Transcranial Direct Current Stimulation Combined With Listening to Preferred Music Alters Cortical Speech Processing in Older Adults.

Emerging evidence suggests transcranial direct current stimulation (tDCS) can improve cognitive performance in older adults. Similarly, music listening may improve arousal and stimulate subsequent performance on memory-related tasks. We examined the synergistic effects of tDCS paired with music listening on auditory neurobehavioral measures to investigate causal evidence of short-term plasticity in speech processing among older adults. In a randomized sham-controlled crossover study, we measured how combined anodal tDCS over dorsolateral prefrontal cortex (DLPFC) paired with listening to autobiographically salient music alters neural speech processing in older adults compared to either music listening (sham stimulation) or tDCS alone. EEG assays included both frequency-following responses (FFRs) and auditory event-related potentials (ERPs) to trace neuromodulation-related changes at brainstem and cortical levels. Relative to music without tDCS (sham), we found tDCS alone (without music) modulates the early cortical neural encoding of speech in the time frame of ∼100-150 ms. Whereas tDCS by itself appeared to largely produce suppressive effects (i.e., reducing ERP amplitude), concurrent music with tDCS restored responses to those of the music+sham levels. However, the interpretation of this effect is somewhat ambiguous as this neural modulation could be attributable to a true effect of tDCS or presence/absence music. Still, the combined benefit of tDCS+music (above tDCS alone) was correlated with listeners' education level suggesting the benefit of neurostimulation paired with music might depend on listener demographics. tDCS changes in speech-FFRs were not observed with DLPFC stimulation. Improvements in working memory pre to post session were also associated with better speech-in-noise listening skills. Our findings provide new causal evidence that combined tDCS+music relative to tDCS-alone (i) modulates the early (100-150 ms) cortical encoding of speech and (ii) improves working memory, a cognitive skill which may indirectly bolster noise-degraded speech perception in older listeners.

Comparing whole-genome shotgun sequencing and DNA metabarcoding approaches for species identification and quantification of pollen species mixtures.

Molecular identification of mixed-species pollen samples has a range of applications in various fields of research. To date, such molecular identification has primarily been carried out via amplicon sequencing, but whole-genome shotgun (WGS) sequencing of pollen DNA has potential advantages, including (1) more genetic information per sample and (2) the potential for better quantitative matching. In this study, we tested the performance of WGS sequencing methodology and publicly available reference sequences in identifying species and quantifying their relative abundance in pollen mock communities. Using mock communities previously analyzed with DNA metabarcoding, we sequenced approximately 200Mbp for each sample using Illumina HiSeq and MiSeq. Taxonomic identifications were based on the Kraken k-mer identification method with reference libraries constructed from full-genome and short read archive data from the NCBI database. We found WGS to be a reliable method for taxonomic identification of pollen with near 100% identification of species in mixtures but generating higher rates of false positives (reads not identified to the correct taxon at the required taxonomic level) relative to rbcL and ITS2 amplicon sequencing. For quantification of relative species abundance, WGS data provided a stronger correlation between pollen grain proportion and sequence read proportion, but diverged more from a 1:1 relationship, likely due to the higher rate of false positives. Currently, a limitation of WGS-based pollen identification is the lack of representation of plant diversity in publicly available genome databases. As databases improve and costs drop, we expect that eventually genomics methods will become the methods of choice for species identification and quantification of mixed-species pollen samples.

Dynamic Useful Field of View Training to Enhance Older Adults' Cognitive and Motor Function: A Pilot Study.

Useful Field of View (UFOV) computerized cognitive training improves older adults' gait speed and balance and reduces dementia risk. We investigated a new form of UFOV training requiring physical movement, Training Under Cognitive Kinematics (TUCK). We hypothesized TUCK would be acceptable, feasible, and potentially efficacious to improve UFOV Test- and motor performance. Sixty-nine older adults were randomized to TUCK, computerized UFOV training, or an active control group. Cognitive- and motor function were assessed before and immediately after the intervention period. Participants rated TUCK as enjoyable, engaging and satisfying, indicating acceptability. Eighty-five percent of participants completed TUCK, demonstrating feasibility. Overall, effect sizes for TUCK did not indicate greater efficacy than computerized UFOV training relative to controls. UFOV training showed effect sizes indicating improved balance as measured by Turn 360 (d=0.37) and Optogait (d=0.51-0.69) from pre- to post- training relative to controls. Incorporating movement into UFOV cognitive training did not enhance cognitive or motor functional gains. Future investigations are needed to elucidate the underlying mechanisms of UFOV cognitive training to enhance motor function. Research should continue to investigate the association of cognitive and motor function and interventions to improve these outcomes among older adults. The trial and planned analyses were pre-registered: https://osf.io/7utgw.

Cognitive Event-Related Potential Responses Differentiate Older Adults with and without Probable Mild Cognitive Impairment.

Background: Older adults rarely seek cognitive assessment, but often visit other healthcare professionals (e.g., audiologists). Noninvasive clinical measures within the scopes of practice of those professions sensitive to cognitive impairment are needed. Purpose: This study examined the differences of probable mild cognitive impairment (MCI) on latency and mean amplitude of the P3b auditory event-related potential. Method: Fifty-four participants comprised two groups according to cognitive status (cognitively normal older adults [CNOA], n = 25; probable MCI, n = 29). P3b was recorded using an oddball paradigm for speech (/ba/, /da/) and non-speech (1000, 2000 Hz) stimuli. Amplitudes and latencies were compared from six electrodes (FPz, Fz, FCz, Cz, CPz, Pz) between groups across stimulus probability and type. Results: CNOA participants had larger P3b mean amplitudes for deviant stimuli than those with probable MCI. Group effects of latency were isolated to deviant stimuli at FCz only when those with unclear P3bs were included. Findings did not covary with age or education. Overall, CNOAs showed a large P3b oddball effect while those with probable MCI did not. Conclusions: P3b can be used to show electrophysiological differences between older adults with and without probable MCI. These results support the development of educational materials targeting professionals using auditory-evoked potentials.

Antiviral therapy: Valacyclovir Treatment of Alzheimer's Disease (VALAD) Trial: protocol for a randomised, double-blind,placebo-controlled, treatment trial.

INTRODUCTION: After infection, herpes simplex virus-1 (HSV1) becomes latent in the trigeminal ganglion and can enter the brain via retrograde axonal transport. Recurrent reactivation of HSV1 may lead to neurodegeneration and Alzheimer's disease (AD) pathology. HSV1 (oral herpes) and HSV2 (genital herpes) can trigger amyloid beta-protein (Aß) aggregation and HSV1 DNA is common in amyloid plaques. Anti-HSV drugs reduce Aß and phosphorylated tau accumulation in cell-culture models. Cognitive impairment is greater in patients with HSV seropositive, and antiviral drugs show robust efficacy against peripheral HSV infection. Recent studies of electronic health records databases demonstrate that HSV infections increase dementia risk, and that antiviral medication treatment reduces this risk. The generic antiviral drug valacyclovir was superior to placebo in improving memory in a schizophrenia pilot trial but has not been tested in AD. METHODS AND ANALYSIS: In patients with mild AD who test positive for HSV1 or HSV2 serum antibodies, valacyclovir, repurposed as an anti-AD drug, will be compared with placebo (lactose pills) in 130 patients (65 valacyclovir and 65 placebo) in a randomised, double-blind, 78-week phase II proof-of-concept trial. Patients on valacyclovir, dose-titrated from 2 g to a targeted oral dose of 4 g daily, compared with placebo, are hypothesised to show smaller cognitive and functional decline, and, using 18F-Florbetapir positron emission tomography (PET) and 18F-MK-6240 PET imaging, to show less amyloid and tau accumulation, respectively. In the lumbar puncture subsample, cerebrospinal fluid acyclovir will be assayed to assess central nervous system valacyclovir penetration. ETHICS AND DISSEMINATION: The trial is being overseen by the New York State Psychiatric Institute Institutional Review Board (protocol 7537), the National Institute on Ageing, and the Data Safety Monitoring Board. Written informed consent is obtained for all subjects. Results will be disseminated via publication, clinicaltrials.gov, media and conferences. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier (NCT03282916) Pre-results.

A Comparison of Behavioral Methods for Indexing the Auditory Processing of Temporal Fine Structure Cues.

Purpose Growing evidence supports the inclusion of perceptual tests that quantify the processing of temporal fine structure (TFS) in clinical hearing assessment. Many tasks have been used to evaluate TFS in the laboratory that vary greatly in the stimuli used and whether the judgments require monaural or binaural comparisons of TFS. The purpose of this study was to compare laboratory measures of TFS for inclusion in a battery of suprathreshold auditory tests. A subset of available TFS tasks were selected on the basis of potential clinical utility and were evaluated using metrics that focus on characteristics important for clinical use. Method TFS measures were implemented in replication of studies that demonstrated clinical utility. Monaural, diotic, and dichotic measures were evaluated in 11 young listeners with normal hearing. Measures included frequency modulation (FM) tasks, harmonic frequency shift detection, interaural phase difference (TFS-low frequency), interaural time difference (ITD), monaural gap duration discrimination, and tone detection in noise with and without a difference in interaural phase (N0S0, N0Sπ). Data were compared with published results and evaluated with metrics of consistency and efficiency. Results Thresholds obtained were consistent with published data. There was no evidence of predictive relationships among the measures consistent with a homogenous group. The most stable tasks across repeated testing were TFS-low frequency, diotic and dichotic FM, and N0Sπ. Monaural and diotic FM had the lowest normalized variance and were the most efficient accounting for differences in total test duration, followed by ITD. Conclusions Despite a long stimulus duration, FM tasks dominated comparisons of consistency and efficiency. Small differences separated the dichotic tasks FM, ITD, and N0Sπ. Future comparisons following procedural optimization of the tasks will evaluate clinical efficiency in populations with impairment.

Quantitative and qualitative assessment of pollen DNA metabarcoding using constructed species mixtures.

Pollen DNA metabarcoding-marker-based genetic identification of potentially mixed-species pollen samples-has applications across a variety of fields. While basic species-level pollen identification using standard DNA barcode markers is established, the extent to which metabarcoding (a) correctly assigns species identities to mixes (qualitative matching) and (b) generates sequence reads proportionally to their relative abundance in a sample (quantitative matching) is unclear, as these have not been assessed relative to known standards. We tested the quantitative and qualitative robustness of metabarcoding in constructed pollen mixtures varying in species richness (1-9 species), taxonomic relatedness (within genera to across class) and rarity (5%-100% of grains), using Illumina MiSeq with the markers rbcL and ITS2. Qualitatively, species composition determinations were largely correct, but false positives and negatives occurred. False negatives were typically driven by lack of a barcode gap or rarity in a sample. Species richness and taxonomic relatedness, however, did not strongly impact correct determinations. False positives were likely driven by contamination, chimeric sequences and/or misidentification by the bioinformatics pipeline. Quantitatively, the proportion of reads for each species was only weakly correlated with its relative abundance, in contrast to suggestions from some other studies. Quantitative mismatches are not correctable by consistent scaling factors, but instead are context-dependent on the other species present in a sample. Together, our results show that metabarcoding is largely robust for determining pollen presence/absence but that sequence reads should not be used to infer relative abundance of pollen grains.

Applying pollen DNA metabarcoding to the study of plant-pollinator interactions.

PREMISE OF THE STUDY: To study pollination networks in a changing environment, we need accurate, high-throughput methods. Previous studies have shown that more highly resolved networks can be constructed by studying pollen loads taken from bees, relative to field observations. DNA metabarcoding potentially allows for faster and finer-scale taxonomic resolution of pollen compared to traditional approaches (e.g., light microscopy), but has not been applied to pollination networks. METHODS: We sampled pollen from 38 bee species collected in Florida from sites differing in forest management. We isolated DNA from pollen mixtures and sequenced rbcL and ITS2 gene regions from all mixtures in a single run on the Illumina MiSeq platform. We identified species from sequence data using comprehensive rbcL and ITS2 databases. RESULTS: We successfully built a proof-of-concept quantitative pollination network using pollen metabarcoding. DISCUSSION: Our work underscores that pollen metabarcoding is not quantitative but that quantitative networks can be constructed based on the number of interacting individuals. Due to the frequency of contamination and false positive reads, isolation and PCR negative controls should be used in every reaction. DNA metabarcoding has advantages in efficiency and resolution over microscopic identification of pollen, and we expect that it will have broad utility for future studies of plant-pollinator interactions.

Chance long-distance or human-mediated dispersal? How Acacia s.l. farnesiana attained its pan-tropical distribution.

Acacia s.l. farnesiana, which originates from Mesoamerica, is the most widely distributed Acacia s.l. species across the tropics. It is assumed that the plant was transferred across the Atlantic to southern Europe by Spanish explorers, and then spread across the Old World tropics through a combination of chance long-distance and human-mediated dispersal. Our study uses genetic analysis and information from historical sources to test the relative roles of chance and human-mediated dispersal in its distribution. The results confirm the Mesoamerican origins of the plant and show three patterns of human-mediated dispersal. Samples from Spain showed greater genetic diversity than those from other Old World tropics, suggesting more instances of transatlantic introductions from the Americas to that country than to other parts of Africa and Asia. Individuals from the Philippines matched a population from South Central Mexico and were likely to have been direct, trans-Pacific introductions. Australian samples were genetically unique, indicating that the arrival of the species in the continent was independent of these European colonial activities. This suggests the possibility of pre-European human-mediated dispersal across the Pacific Ocean. These significant findings raise new questions for biogeographic studies that assume chance or transoceanic dispersal for disjunct plant distributions.

An rbcL reference library to aid in the identification of plant species mixtures by DNA metabarcoding.

PREMISE OF THE STUDY: DNA metabarcoding has broad-ranging applications in ecology, aerobiology, biosecurity, and forensics. A bioinformatics pipeline has recently been published for identification using a comprehensive database of ITS2, one of the common plant DNA barcoding markers. There is, however, no corresponding database for rbcL, the other primary marker used in plants. METHODS: Using publicly available data, we compiled a reference library of rbcL sequences and trained databases for use with UTAX and RDP classifier algorithms. We used this reference library, along with the existing bioinformatics pipeline and ITS2 reference library, to identify species in an artificial mixture of nine species of pollen. We have made this database publicly available in multiple formats, to allow use with multiple bioinformatics pipelines, now and in the future. RESULTS: Using the rbcL database, in addition to the ITS2 database, we succeeded in making species-level identifications for eight species and a family-level identification of the ninth species. This is an improvement on ITS2 sequence alone. DISCUSSION: The reference library described here will assist with identification of plant species using rbcL. By making another gene region available for standard barcoding, this will increase the resolution and accuracy of identifications.

Pollen DNA barcoding: current applications and future prospects.

Identification of the species origin of pollen has many applications, including assessment of plant-pollinator networks, reconstruction of ancient plant communities, product authentication, allergen monitoring, and forensics. Such applications, however, have previously been limited by microscopy-based identification of pollen, which is slow, has low taxonomic resolution, and has few expert practitioners. One alternative is pollen DNA barcoding, which could overcome these issues. Recent studies demonstrate that both chloroplast and nuclear barcoding markers can be amplified from pollen. These recent validations of pollen metabarcoding indicate that now is the time for researchers in various fields to consider applying these methods to their research programs. In this paper, we review the nascent field of pollen DNA barcoding and discuss potential new applications of this technology, highlighting existing limitations and future research developments that will improve its utility in a wide range of applications.

Review and future prospects for DNA barcoding methods in forensic palynology.

Pollen can be a critical forensic marker in cases where determining geographic origin is important, including investigative leads, missing persons cases, and intelligence applications. However, its use has previously been limited by the need for a high level of specialization by expert palynologists, slow speeds of identification, and relatively poor taxonomic resolution (typically to the plant family or genus level). By contrast, identification of pollen through DNA barcoding has the potential to overcome all three of these limitations, and it may seem surprising that the method has not been widely implemented. Despite what might seem a straightforward application of DNA barcoding to pollen, there are technical issues that have delayed progress. However, recent developments of standard methods for DNA barcoding of pollen, along with improvements in high-throughput sequencing technology, have overcome most of these technical issues. Based on these recent methodological developments in pollen DNA barcoding, we believe that now is the time to start applying these techniques in forensic palynology. In this article, we discuss the potential for these methods, and outline directions for future research to further improve on the technology and increase its applicability to a broader range of situations.

The history of introduction of the African baobab (Adansonia digitata, Malvaceae: Bombacoideae) in the Indian subcontinent.

To investigate the pathways of introduction of the African baobab, Adansonia digitata, to the Indian subcontinent, we examined 10 microsatellite loci in individuals from Africa, India, the Mascarenes and Malaysia, and matched this with historical evidence of human interactions between source and destination regions. Genetic analysis showed broad congruence of African clusters with biogeographic regions except along the Zambezi (Mozambique) and Kilwa (Tanzania), where populations included a mixture of individuals assigned to at least two different clusters. Individuals from West Africa, the Mascarenes, southeast India and Malaysia shared a cluster. Baobabs from western and central India clustered separately from Africa. Genetic diversity was lower in populations from the Indian subcontinent than in African populations, but the former contained private alleles. Phylogenetic analysis showed Indian populations were closest to those from the Mombasa-Dar es Salaam coast. The genetic results provide evidence of multiple introductions of African baobabs to the Indian subcontinent over a longer time period than previously assumed. Individuals belonging to different genetic clusters in Zambezi and Kilwa may reflect the history of trafficking captives from inland areas to supply the slave trade between the fifteenth and nineteenth centuries. Baobabs in the Mascarenes, southeast India and Malaysia indicate introduction from West Africa through eighteenth and nineteenth century European colonial networks.

New genetic and linguistic analyses show ancient human influence on baobab evolution and distribution in Australia.

This study investigates the role of human agency in the gene flow and geographical distribution of the Australian baobab, Adansonia gregorii. The genus Adansonia is a charismatic tree endemic to Africa, Madagascar, and northwest Australia that has long been valued by humans for its multiple uses. The distribution of genetic variation in baobabs in Africa has been partially attributed to human-mediated dispersal over millennia, but this relationship has never been investigated for the Australian species. We combined genetic and linguistic data to analyse geographic patterns of gene flow and movement of word-forms for A. gregorii in the Aboriginal languages of northwest Australia. Comprehensive assessment of genetic diversity showed weak geographic structure and high gene flow. Of potential dispersal vectors, humans were identified as most likely to have enabled gene flow across biogeographic barriers in northwest Australia. Genetic-linguistic analysis demonstrated congruence of gene flow patterns and directional movement of Aboriginal loanwords for A. gregorii. These findings, along with previous archaeobotanical evidence from the Late Pleistocene and Holocene, suggest that ancient humans significantly influenced the geographic distribution of Adansonia in northwest Australia.

Isolation, via 454 sequencing, and characterization of microsatellites for Vachellia farnesiana (Fabaceae: Mimosoideae).

PREMISE OF THE STUDY: We isolated 15 polymorphic microsatellite markers from Vachellia farnesiana for use in population genetic studies to determine the native range of the species. • METHODS AND RESULTS: Initially, 454 shotgun sequencing was used to identify and design primers for 68 microsatellite loci. Of these, we trialed 47 loci in the target species, and 42 (89%) amplified a product of expected size. Fifteen of the 47 loci were screened for variation in 21 individuals from the native range of V. farnesiana in southern Mexico and 20 from northwestern Australia. Fourteen loci were polymorphic, with observed heterozygosity ranging from 0.026 to 1.00 (mean = 0.515) and two to 12 alleles per locus (average = 5.2). Cross-amplification was successful in four to 11 loci in three other Vachellia species. • CONCLUSIONS: The new microsatellite loci will be useful in understanding genetic variation and investigating the role of human-mediated dispersal in the current distribution of V. farnesiana.