Interpreting Life-History Traits of Miconia (Miconia calvescens) through Management over Space and Time in the East Maui Watershed, Hawaii (USA)

Abstract

Miconia (Miconia calvescens DC) was introduced to the East Maui Watershed (EMW) a half-century ago with more than 25 yr of management recorded. Using a historical spatiotemporal data set, we constructed a leptokurtic dispersal kernel with 99% of progeny confined to within 549 m of the nearest maternal source and the remaining 1% dispersed out to 1,636 m. Seedbank persistence, based on postdated recruitment, displayed an exponential decay projecting extinction beyond 20 yr. These parameters are highly congruent to independent interpretations of M. calvescens in Australia and Tahiti. In a simulated stage matrix model, we projected management efforts to locally eradicate a small incipient propagule bank wherein optimal management was achieved with an annual harvest rate that eliminated all juvenile recruits before reaching maturity, until extinction. Based on current pricing for helicopter herbicide ballistic technology (HBT) operations, the optimal, variable cost to locally eradicate this incipient propagule bank was estimated to be less than US$42,000, with ~90% of the effort searching for the most distant 1% of the progeny expended within the first 9 yr after the mature discovery. This variable cost was sensitive to seedbank size, recruitment rate, and dispersal range, but was most sensitive to harvest rates between suboptimal and excess. In a scenario prioritizing the upper region of EMW, we retroactively analyzed past HBT efforts eliminating satellite M. calvescens and determined that 27% of the total effort resulted in 87% of the total protection to this priority asset, with every US$1 invested potentially avoiding US$184 in future costs. Management outside the priority area was less economical, with returns in protection diminishing with distance from the priority upper region. Miconia calvescens is currently not eradicable in the EMW, and full containment of the invasion would require a substantial increase in stable, long-term funding. With limited resources, local eradication of satellite M. calvescens could be the most cost-effective alternative to protecting uninvaded areas prioritized for critical ecosystem functions.

Comparing Interpretation of High-Resolution Aerial Imagery by Humans and Artificial Intelligence to Detect an Invasive Tree Species

“…Developing a DNN with perfect accuracy in miconia detection is improbable and may not be necessary, based on the biology and life history traits of the species. Strategically, management interventions must outpace invasion by eliminating miconia before it reaches maturity within 3-4 years of germination [32]. Seed bank germination is asynchronous and can survive for multiple decades [32,33], and miconia can remain cryptic in the understory for some time before becoming visible from above.…”

“…Strategically, management interventions must outpace invasion by eliminating miconia before it reaches maturity within 3-4 years of germination [32]. Seed bank germination is asynchronous and can survive for multiple decades [32,33], and miconia can remain cryptic in the understory for some time before becoming visible from above. Thus, even with the capability of 100% target detection, there is an inherent commitment to repeated surveillance of an area to ensure extinction.…”

“…Miconia is an autogomous species that is prone to passive long-distance dispersal by frugivores [27] and capable of establishing isolated founder populations stochastically spread out over large areas [28,29]. Moreover, seed from several miconia species are reported with extended physiological dormancy that results in latent germination and persistent recruitment from a deposited seedbank over several decades [30,31], a trait also specifically observed in miconia [32,33]. Miconia can germinate in low light conditions and can remain visually hidden under a multi-tiered forest canopy for several years [24,31].…”

“…Miconia can germinate in low light conditions and can remain visually hidden under a multi-tiered forest canopy for several years [24,31]. These life-history traits make miconia a highly problematic and aggressive invasive species, despite arduous search efforts and long-term intervention schedules [32].…”

Seed-bank dynamics of native and invasive Impatiens species during a five-year field experiment under various environmental conditions

“…In addition, seed banks maintain population genetic diversity, and thus improve the ability of alien species to respond to novel site conditions encountered in the introduced range by spreading the environmental risks over time (Gioria et al 2012). The role of seed banks in population persistence has to be taken into account during eradication, because a few viable seeds in the soil may allow re-invasions (Fletcher et al 2015, Leary et al 2018, Moravcová et al 2018.…”