Comments on CBST draft document
Sally Aitken, April 15, 2015
1) I have provided a draft schematic diagram that I think would help the lay reader
better understand the options for seed zones.
2) One concern frequently expressed by ecologists and conservation biologists is
that the relationship between tree genetics and populations of symbionts and
pathogens or parasites will be disrupted by climate based seed transfer. Nothing
is mentioned about this in this report. Some people also worry about
outbreeding depression – this is not a substantial risk with trees or the transfer
distances you are talking about, but it should be acknowledged, and literature
cited that support dismissing this as a concern. I rather self-servingly suggest you
consider referencing Aitken and Whitlock 2013, and Aitken and Bemmels
(submitted) as these papers directly address these issues.
3) P. 13 - I am concerned that by ignoring asymmetry in local adaptation, you are
giving up productivity that could be captured if you recognize such asymmetry.
There is both theoretical and empirical support for asymmetric gene flow in
continuously distributed, ‘abundant centre’ species, whereby you expect
populations inhabiting colder than average conditions for a species to be
optimally adapted to warmer climates than they inhabit, and populations that
inhabit warmer than average conditions for a species to be optimally adapted to
cooler conditions than they inhabit (see Aitken and Whitlock 2013, supplemental
materials, and references therein for the theory). I know that much of your own
provenance trial data supports this result. Figure 1 also shows this for lodgepole
pine, where quite a few sources with a negative transfer distance have better
than local performance. Can’t the transfer functions be adjusted somewhat to
reflect this lack of local optimum, without dramatically changing the approach?
4) P 13 – continued – I can’t help but wonder if superior provenances are those that
should be targeted given the uncertainties around climate change. The data
from the Illingworth trial, at least at age 20, were quite convincing about their
performance over a wide range of sites. We are currently analyzing whether
these come from environments that tend to have different patterns of temporal
variability, or whether they tend to be populations with high genetic diversity.
I’m not clear on whether you will maintain class B+ provenance recognition in
the new approach, although P. 13 suggests that you won’t. Do you need to give
these up under the new system? You would only need to give them a genetic
suitability >1.0 – this could easily be built into the software, I would think.
5) Does the Douglas-fir example in your report refer to coastal Douglas-fir only?
This should be made clear.
6) P. 12 – which 9 climate variables did you retain? When a pair of climate variables
was strongly correlated, how did you decide which to retain?
7) P. 15 – “Use of a transfer function response trait that is more strongly related to
fitness than is height” – delete second “is”
8) P. 16, Figure 3 and elsewhere – “Distance matrix” or “Euclidean distance” should
be called “Climate distance matrix” or “Euclidean climate distance” to avoid
confusion with geographic distance. What time period does this analysis assume
you are matching for climate?
9) P. 17 – Csaba Matyas has come to a similar conclusion in terms of timing – 1/3
rotation. On the other hand, Christine Dean of Weyerhauser recently said about
coastal Douglas-fir “the winners are determined by age 5” (but they are not
thinking about climate change much).
10) All tables – Table caption should go above tables; Figure captions below figures. I
have no idea why, but that is the convention.
11) Table 4 – again, specify climate distance, not just distance. Tables and figures
should be stand alone and will be taken out of context if viewed at a glance
without a careful read.
12) Section 7.2 – again, important here to add “climate” in front of “distance”
throughout.
13) P. 19 – “applying slightly lower limits to each genetic suitability class for orchard
seedlots than for natural stand seedlots” – how did you determine this
adjustment? Analysis? Rule of thumb? Approximation? (Our results from
AdapTree show that seed orchard lots may actually show stronger local
adaptation than wildstand lots, on average, but these results aren’t finalized yet
– stay tuned.)
14) P. 19 (cont’d). “Fortunately, the mean climates of test sites and parents are
usually very similar in BC (See Appendix 1 in O'Neill et al. 2008b). Consequently,
the optimum deployment climate for orchard parents should be relatively
unaffected by testing and selection.” This seems like a leap – you are assuming
selection has not affected adaptive traits. I would be a little more circumspect
about this (see point 12) above.
15) P. 19 “at the test site climate mean”. Reword since GW values are estimated
using data on families from multiple sites. This sounds like progeny tests are
conducted at a single site.
16) Top of p. 20 Some growth and yield studies have found productivity is increasing
at quite a few sites. Most people predict declines in the longer term, but in the
shorter term, I expect quite a few cooler sites with populations that are
optimally adapted to warmer than local conditions to increase in productivity. I
think that precipitation is the real wild card. Also, see Wang et al. 2006.
17) P. 20 – section 9.0 – this needs to come way sooner, and potentially be
expanded upon as these provenances may be very valuable in variable new
climates (see all my comments about B+ seedlots above).
18) Recommendations: Change “hybrid zone” name to something else – why not
simply climate-based seed transfer system? Insert “climatic” in front of distance
throughout.
19) Figure 4 is excellent (with a few edits for hybrid zone, distance, etc.)
20) I would like to see something in the conclusions and recommendation about
how new knowledge will be incorporated into populating and refiinng the
matrices for all species (i.e., how can we use AdapTree data to help refine this
system?) We are very close to having a great deal of data with which to inform
the matrices, or to evaluate the effects of CBST in terms of genetic composition
and diversity. Finally, I think that one recommendation should be to evaluate the
predicted productivity under this CBST system compared to the status quo –
perhaps a case study with one or two species?
Good work! I hope these comments are helpful.