Acacia longifolia: A Host of Many Guests Even after Fire

Acacia longifolia is a worldwide invader that cause damage in ecosystems, expanding largely after wildfires, which promote germination of a massive seed bank. As a legume, symbiosis is determinant for adaptation. Our study aims to isolate a wider consortium of bacteria harboured in nodules, including both nitrogen and non-nitrogen fixers. Furthermore, we aim to evaluate the effects of fire in nodulation and bacterial diversity on young acacias growing in unburnt and burnt zones, one year after the fire. For this, we used molecular approaches, M13 fingerprinting and 16S rRNA partial sequencing, to identify species/genera involved and δ15N isotopic composition in leaves and plant nodules. Nitrogen isotopic analyses in leaves suggest that in unburnt zones, nitrogen fixation contributes more to plant nitrogen content. Overall, A. longifolia seems to be promiscuous and despite Bradyrhizobium spp. dominance, Paraburkholderia spp. followed by Pseudomonas spp. was also found. Several species not previously reported as nitrogen-fixers were identified, proposing other functions besides ammonia acquisition. Our study shows that bacterial communities are different in nodules after fire. Fire seems to potentiate nodulation and drives symbiosis towards nitrogen-fixers. Taken together, a multifunctional community inside nodules is pointed out which potentiate A. longifolia invasiveness and adaptation.

Supporting Essential Biodiversity Variables: The GLOBIS case study

Essential Biodiversity Variables (EBVs) are the latest push toward supporting state of the environment indicators (Pereira et al. 2013). The European Union Funded Creative-B Project (see https://cordis.europa.eu/project/rcn/100345/brief/en) outlined the status and strategy for interoperability between what they termed Biodiversity Research Infrastructures (BRIs: such as the Global Biodiversity Information Infrastructure (GBIF), the Atlas of Living Australia (ALA) and the Integrated Digitized Biocollections (iDigBio)). Toward the end of that project, the group decided that a logical follow-on project should position BRIs to support the production of Essential Biodiversity Variables (EBVs). This idea became the GLOBal Infrastructures for Supporting Biodiversity research (GLOBIS-B) project (http://www.globis-b.eu) and this presentation provides a summary of a case study on generating EBVs (Hardisty et al. 2019). As a part of GLOBIS-B, I suggested that a small team of GLOBIS members should document in detail, each step in the production of an EBV from GBIF and the ALA data for a few invasive species. We wanted address the rarity of detailed recording and justification for each step in the production of a dataset for environmental evaluation. I anticipated that the team would encounter many practical issues, but this case study raised far more significant issues that any of us had anticipated. The EBV chosen for this study was Area of Occupancy (IUCN Standards and Petitions Subcommittee 2017) and the species selected represented various invasion scenarios: Acacia longifolia; Vespula germanica and Bubulcus ibis. The workflow included 20 steps between locating data and publishing an EBV, and these steps were radically different between GBIF and the ALA. The workflow required manual steps such as resolving invasive status of Acacia longifolia subspecies; only one of which was ‘invasive’. Datasets of occurrence records had to be exported from the ALA and GBIF to enable filtering for purpose, for example, not all Darwin Core terms are exposed in the current public interface of the ALA. After the record filtering, the ALA and GBIF datasets then required merging and deduplication, for which one-off code had to be written. A few of the 15 significant messages from this study included: a lack of consistency of data between BRIs (e.g., GBIF records should be a superset of ALA records); consistency and adequacy of filtering tools between BRIs; exported data structures massively differed between BRIs; that automation of the workflows may be possible but many manual intervention steps were required. By my figuring, the case study took approximately 10 times longer than anticipated, but the messages to BRIs was clear – consistency and adequacy of data and tools require urgent work.

The germination success of Acacia longifolia subsp. longifolia (Fabaceae): a comparison between its native and exotic ranges

Acacia longifolia subsp. longifolia is native to South-eastern Australia and has naturalised in many regions across the globe, including in Portugal, Spain, and South Africa invading extensive areas. Prolific seed production and a long-lived seedbank are considered key factors that enhance its invasiveness. Yet, the effects of different factors on germination are still underexplored. Seeds were collected from Portuguese and Australian populations, and germination was evaluated under different temperature regimes, photoperiods, pH levels, salt stress, osmotic potential and burial depths. Findings show both populations share some similar patterns but also reveal important differences related to their germination. Higher temperatures induce increased germination rates while the photoperiod has no effect on germination. Both populations had quicker seed emergence under dark conditions. Seeds from both populations decrease germination rate under increasing salt-stress and show a wide range of pH tolerance, but Australians seeds are more tolerant to increase of both parameters. Seeds from the Portuguese population are bigger and germinated from deeper depths than the Australian. Our results may provide information to improve management of this species seedbank. Germination can prevent by, tillage or other interventions that help to increase burial depths; adding lime (to increase the soil alkalinity) can reduce its germination rate in both geographical ranges.