iHerp_Australia_-_November_-_December_2018

Spotted Genet (Genetta genetta) - are also frugivorous
and may contribute to seed dispersal of C. tricoccon,
studies have clearly revealed the superiority of the
endemic lizards in this role. The genets, like many
other mammals, defecate in latrines, which are located
in sites unsuitable for germination, like caves. This also
leads to clumping of the seeds, which has negative
impacts on germination and survival.

Lizard pollinators are also threatened by introduced
invertebrates and plant species. On Mauritius, the
endemic Blue-tailed Day Gecko (Phelsuma cepediana)
visits flowers of 12 plant species, and is the main
visitor of three. It is considered vital to the reproduc-
tion of endemic, endangered plant species, including
Trochetia blackburniana and Roussea simplex, of which
it is the sole pollinator. But the introduced European
Honeybee (Apis mellifera) also visits 10 of the same
plant species visited by P. cepediana, posing a threat
through competition for shared resources. Research-
ers have also observed honeybees acting aggressively
towards P. cepediana when feeding on Pandanus
barklyi.

Additionally, both the pollination and seed dispersal
services P. cepediana performs when foraging on the
critically-endangered R. simplex are threatened by the

invasive ant Technomyrmex albipes. This extremely

aggressive species will attack P. cepediana (or any

other animal) within their vicinity. Moreover,

T. albipes further excludes P. cepediana from accessing

flowers by building galleries of dirt around nectar, and

disrupts gecko seed dispersal by tending honeydew-

producing mealybugs on R. simplex fruits. Seed set of

ant-infested flowers has been proven to be vastly

impaired, and very few seeds are ingested and

dispersed by geckos if fruits have ants on them,

creating dire implications for the conservation of

R. simplex.

Sometimes, conservation of the interactions between

lizards and the flowering plants they visit requires the

removal of exotic plants. The conservation of native

plants – even those that are not endangered – may also

be important in providing appropriate habitat. Not

only has P. cepediana been found to be more common

where exotic plants have been removed, but it is also

reliant on patches of Pandanus palm for habitat and

shelter. Studies have found that visitation rates of

P. cepediana to endemic Mauritian plants significantly

decreased with distance from Pandanus patches,

leading to reduced reproductive success of the plants

concerned.

Although exotic species typically pose a serious threat

to lizard-plant mutualisms, a gecko endemic to

Reunion Island, Phelsuma inexpectata, has been

consistently observed to rob pollen pellets from

introduced European Honeybees as they foraged on

flowers. Over a period of 140 minutes, a total of 78

attempts at pollen theft were recorded, of which 40%

were successful.

Some plant species are obligatorily dependent on

saurochory. For example, seeds of Melocactus violaceus

will only break dormancy if they pass through the

digestive tract of a lizard, making their seed dispersal

agent, the Amazon Lava Lizard (Tropidurus torquatus)

indispensable. The seeds of Spondias mombin are

unusually large, measuring 20mm across, and hence

are unlikely to be dispersed by small animals or wind.

However, 79 seeds from this plant species were

discovered in the gut of a single Green Iguana (Iguana

iguana). The Green Iguana has been implicated in the

dispersal of seed from over 35 different plants, and

ingestion of seed by the lizards has also been shown to

significantly increase both the success and rate of

germination for some species. Higher germination

rates (and thus enhanced chances of survival) have

been reported for other frugivo-

rous lizards: in one trial, 90.7%

of Ziziphyus rignoni seeds

ingested by Rhinoceros Iguanas

(Cyclura cornutua) and Ricord’s

Rock Iguanas (C. ricordii) germi-

nated after 8 days, compared

with just 3.7% for controls.

Another study found that

Pithecellobium juliflora seeds that

had passed through the gut of the

Mexican Spiny-tailed Iguana (Ctenosaura pectinata)

had significantly lower bruchid infestations (32.7% for

ingested vs 94.6% for controls).

Even when successful germination is unaffected or

negatively impacted by the passage of seed through a

lizard’s digestive tract, it cannot be concluded that the

reptile does not contribute to seed dispersal. Seeds are

‘The GREEN IGUANA has been

implicated in SEED DISPERSAL of over 35

PLANTS, and ingestion of seed by the lizards

ENHANCES GERMINATION.’

Green Iguana (Iguana iguana). Image by

Andrey Shcherbukhin.