The New Zealand Plant Conservation Network

Big call Mike although I can see where you are coming from.
I don't know the science but I have thought about the Kereru dispersal issue and it didn't seem logical that this was the only way.
My theory is that it was the Moa that may have spread the Karaka. Once they became extinct Karaka simply survived in groves where seed fall kept the population growing. Obviously Maori moved it about a lot making it hard to tell what is natural and what is not. Has anyone compared the composition of the poison from Karaka to C. disimilis ? If they were the same it would suggest a likely possibility that it was brought here....?

HI Andre, to my knowledge no fruits larger than matai seed have been found intact in moa stomach remains. Moa tended to have crops full of gizzard stones. The karaka seed mesocarp resembles the husk of a peanut - it is not robust and I wouldn't have thought that it sufficiently protects the seed while passing through the gut. I personally very much doubt that moa were significant seed dispersers of any of our large fruited species because the seeds would have been damaged in the gizzard, except perhaps puriri which has a very hard seed.

@mike just reading the comment again re seed trapping - the seed traps were placed beneath large fruited species, that included karaka. Not much movement of karaka into seed traps beneath other species if I recall that correctly. Kahikatea had the largest dispersal distance - no seedfall traps placed beneath kahikatea but most seedfall traps got some of its seeds.

Hi Andre, as Astrid notes - the seed of karaka is unlikely to survive the gizzard stones in moa. Individual stones could weigh up to 500g in some species. See Thorsen et al. 2011. Faunal influences on NZ seed dispersal characteristics. Evolutionary Ecolgy 25: 1397-1426. In that paper I postulate that the large gizzard stones would have selected for small seeds which could survive in the interstitial spaces. That why no moa adapted fruit in NZ?

Chemical composition would be interesting, but plants develop chemical defences for a variety of reasons, and not usually to deter dispersers (that would be counterproductive). It is more likely to prevent either insects consuming the flesh or mammals stripping fruit before it is ripe (fruit bats are present on the New Caledonian home of C. disimilis).

@ Astrid - karaka being trapped predominantly under its own canopy fits with my observations that seedlings a very rarely found more than 10m from an adult tree. Must finish writing that pape

Mike would you mind sending me a copy of your papers? Thanks
astrid @at wildlands.co.nz

I still struggle how to comprehend that an endemic New Zealand lineage (Corynocarpus laevigatus) with a fossil record stretching back to the Miocene can be introduced to New Zealand Mike! Genetic similarity I would expect for a Australian - Zealandia element but I would not use that as evidence that the distinct C. similis and C. laevigatus were potentially conspecific, nor to infer a 'recent' introduction to New Zealand - others have said that and they were shown to be wrong. I agree with Brian Molloy and Steve Wagstaff here. Corynocarpus laevigatus is a northern North Island (New Zealand) endemic. Further a PhD student (Robyn Atherton) I co-supervised with Lara Shepherd and Peter Lockhart has data that shows dispersal from N.Z. to the Chathams and Kermadecs and also supports our view this tree is endemic. This is being written up for a paper.

hi Peter, my questioning of the indigenousness of karaka came out of PhD which will be published sometime. I agree the Miocene leaf fossil is evidence against a human arrival, but it also only shows that a karaka-like member of the Corynocarpaceae was present in the Miocene when NZ had a much more tropical climate which fits the distribution of the rest of the family. It is not proof in itself of a lineage stretching back to the Miocene as there are other potential explanations - such as its extinction around the Oligocene (as with other plant families in NZ). Genetic data that does not further investigate extra-NZ species doesn't help either hypothesis. Wagstaff and Dawson's paper note very low genetic variability for a species that has been here since the Miocene. The same as my ecology-based hypothesis would have to account for genetic data, genetic data would have to account for the observations that karaka in NZ is not a frequent element of the diet of its presumed main ....

... disperser and regeneration patterns that do not match those of other large fruited species in northern NZ except on the one island where pigeons are absent.

HI All, I think this discussion is really interesting. Do any of you object if I put the conversation in the next Trilepidea ? Happy for bits to be trimmed out if you'd rather

The Oligocene is older than the Miocene - so I don't follow your argument about something that has fossils here in the Miocene going extinct in the Oligocene - do you mean it arrived twice? This also depends on when in the Miocene something arrived - I did not say that C. laevigatus as a species stretches back to the Miocene I said that the lineage does - and this is a very different concept. Further just because there is little genetic divergence between species does not mean they are the same, or what not it more often means that the markers used are not as discriminating for that sort of question - and the ones that Wagstaff used are not ideal for looking at species divergance. Morphologically no one is saying that C. similis (look at the epithet) and C. laevigatus are not similar, and I would expect them to be allied but they are not the same either - and I infer from your statements you are suggesting that they are. Robyn's admittedly as yet unpublished work used better DNA..