On 18 September, 2017, Hurricane Maria, a category 5 hurricane with 270 kph winds, passed directly over the island of Dominica, West Indies. The storm was the worst natural disaster in the island’s history, and destroyed the forest canopy as well as much of the understory vegetation (see below).
Destruction of rain forest canopy along the Castle Bruce Road, Dominica, April, 2018.
I surveyed Dominica from April to June 2018, approximately seven months after the hurricane. Heliconia caribaea and H. bihai are normally at peak flower during this period, but their flowering was absent except for a few plants that grew in areas isolated from the storm. Heliconia wagneriana, an introduced species native to Central America, however, was at peak flower and served as the primary food source for purple-throated caribs.
Fig. 1. Bills of female (A) and male (B) purple-throated caribs and flowers and inflorescences of the native Heliconia bihai (C, E) and H. caribaea (D, F, G) and introduced H. wagneriana (H, I).
Whereas prior to the hurricane, we found that female purple-throated caribs were the sole visitor to the long flowers of H. wagneriana, following the hurricane, we found that male purple-throated caribs were the most frequent visitor to H. wagneriana. The mismatch between a short-billed pollinator and a long-flowered plant resulted in strong natural selection for shorter flowers in H. wagneriana, because males could only access nectar from plants with short flowers (see below).
Fig. 2. Relationships between seeds per plant (A, B) and visits per plant (C, D) to corolla length for populations of H. wagneriana before and Hurricane Maria. (A) Selection on corolla length before hurricane in the 2017 Castle Bruce (CB) and Macoucherie (M) populations. (B) Selection on corolla length after hurricane in the 2018 Layou (L) and Macoucherie (M) populations. (C) Visits to corolla length pre-hurricane in the 2017 Castle Bruce (CB) and Macoucherie (M) populations. (D) Visits to corolla length after hurricane in the 2018 Layou (L) and Macoucherie (M) populations.
We estimated a roughly 75% decrease in the population size of A. jugularis, and results suggest the heaviest mortality occurred among short-billed male hummingbirds and larger-bodied individuals of both sexes, which would have higher nectar requirements and the most difficulty obtaining nectar (see below). (This work was published as Temeles and Bishop 2019 Biotropica, with honors student Gabriella Bishop).
Fig. 3. Bill, wing, and tarsus lengths of male (A-C) and female (D-F) A. jugularis before and after Hurricane Maria. (A) Male bill length. (B) Male wing length. (C) Male tarsus length. (D) Female bill length. (E) Female wing length. (F) Female tarsus length. All differences before and after the hurricane are significant (P’s < 0.05) with the exception of female bill length.
I surveyed Dominica again from May through June 2019. Native heliconias were in flower, although peak flowering was delayed and occurred later in the year (June as opposed to April). Spent inflorescences indicated that Heliconia caribaea flowered from November 2018 to January 2019, which is very unusual; the usual flowering period of this Heliconia is from January to July.
Hummingbird populations are still greatly reduced and no more than 25% of pre-hurricane levels, and less than 10% at some locations (e.g., Boeri Lake). Pollinator visits were 10% – 30% of pre-hurricane levels, and resulting seed set per plant ranged from 2.5% to 20% of pre-hurricane levels.