ABOVE: Artocarpus fruiting gregariously at Sepilok in October 2014. Left to right; A. tamaran, A. dadah, A. kemando, A. limpato.

Artocarpus species such as  Jackfruit (A. heterophyllus) Cempedak ( A. intger) and Terap  (A. odoratissimus)  are such prolific fruiters that it is obvious to any casual observer that there is a tendency for these species to  fruit  simultaneously  during the annual fruiting season in Borneo.

There are two well researched reasons for  gregarious fruiting (masting);

  1. So that male pollen will be able to land on receptive female stigmas on an unrelated tree, instead of being wasted.  Note that Artocarpus species are monoecious with separate male and female flowers on the same tree.  However male flowers  do not produce pollen whilst female flowers on the same tree are receptive. This means  that Artocarpus are “obligate outcrossers” and cannot self pollinate.
  2. So that the local Artocarpus seed predators eg squirrels, langurs  will be overwhelmed with food when the crops ripen simultaneously and some seeds at least will survive.

However ,casual observation also tells us that  wild species of Artocarpus are more likely to fruit together simultaneously whilst the more common cultivated species may fruit sporadically throughout the year presumably because of human selection of cultivars which fruit “out of season”.

Several different studies of  the foraging by the Dawn Nectar Bat  Eonycteris spelea  have shown that  Artocarpus  nectar and pollen is an important part of their diet.

At the Batu caves near Kuala Lumpur, Start ( 1974) and (1976)  found that  Artocarpus  pollen was present in E. spealea feces  almost continuously throughout the year  whilst other sources of food such as Sonneratia, Durio and Parkia  flowered more sporadically.

Start (1974) PHD The feeding biology of nectarivorous bats Chiroptera Macroglossinae in Malaysia

Start, A.N., & Marshall A., (1976) Nectarivorous bats as pollinators

Also at the Batu Caves  Lim and Wilson (2018)   by analyzing the DNA of plant remains in E. spelea feces found that A. heterophyllus was the most regular  provider of nectar and polen. A.  heterophyllus (Jackfruit) is widely cultivated in home orchards around Kuala Lumpur.

Lim & Wilson (2018) Plants eaten by E. spelea at Batu caves Final

Prior to these studies botanist believed that Artocarpus was either wind pollinated or pollinated by specialized beetles feeding on a fungus that grew on Artocarpus flowers.

Sakai (2000) Artocarpus pollination at Lambir