The three branches of humanity are arguably separate species; interbreeding generally doesn't happen without technological assistance. This is almost certainly deliberate on the part of the Precursors, hence the dispute over whether it qualifies (along with differences in the definitions of "species.")
Zhdez are quite willing to "fix" the genes that prevent it, Terrans generally see this as a threat, and Inukari are ambivalent - when it happens, they tend to refer to "half-Zhdez heritage" and the like. Zhdez don't differentiate: you are who you identify as.
Uplifting
I am waffling over the lack of aliens, and considering uplifted Terran/etc. species: dolphins, gorillas, corvids, things of that nature.
I also feel like Gvazda would have domesticated their monkey-analogs the instant they were contacted by humans. Not sure they'd uplift them though.
Zhdez seem like the most likely to (I'm still leaning toward them having higher technology, though being reluctant to let it outside their own territory), and also to treat uplifted beings as equals. Which means you'd be less likely to encounter them outside Zhdez territory, not because they're controlled tech so much as because they wouldn't care to be treated as less-than. So they've almost certainly got catfolk of some sort, which will be interesting at first contact with the lionfolk east of the Gvazda.
Uplifted dolphins being gangsters on Melodite would be... interesting.
Jump fields/shields
Update: There is now a wiki entry for jumpdrives, which supercedes this.
I think the jump field is going to be necessary as a protective shield, much as I don't care for that idea. Naked matter in jumpspace is like blood in the water, and attracts predators. Mainly tiny parasites that nibble away at matter, so leaving the field down invites progressive etching of the hull and sensors and things. But there's also the risk of larger things.
I feel like this makes whales just another predator, though, and I'm not sure how I feel about that.
Jonah and the whale
Update: There is now a wiki entry for jumpdrives, which supercedes this.
I'm contemplating the idea that jump fields are impermeable, though that sort of starts to sound like Star Trek shields. But it allows for things like: a predator has to engulf its prey, through either a temporary or permanent opening in its own field, then break down the prey's shield. If it hasn't already, that is, though being able to grab the prey beforehand eliminates the possibility of shark/hyena analogs grabbing some of the spoils.
Which then leads me to think: what if a whale swallows a starship and then sounds?
Hmm.
Navigation
Update: There is now a wiki entry for jumpdrives, which supercedes this.
If you don't navigate via the gates, how do you navigate? I'm already at risk for "currents" being a sort of "stargate" situation, so I don't want it to be "follow the currents to the gate confluences" if I can help it.
It is possible that sensors can pick up the gates (possibly via field harmonics or something - perhaps shutting off one's drive field lets one "go dark" but also means you lose your ability for long-range sensing?)
I think aside from bioluminescent creatures, jumpspace is dark (hence "voidspace"), so that rules out visual sightings until you're close enough to a correspondence zone.
I'd like it to be something like sailing ships: compass and sextant, and if you're in a storm you might not know how far off course you are, and even if it's just cloudy you might not be entirely sure you're in the right place.
Hmm.
RIP the false star
While I think there will still be a glow from tiny organisms marking the correspondence point of each realspace mass, I think I'm going to drop the idea of the hallucinatory light and false star and so forth. This does mean I have the option of bot craft, which might be necessary in some cases: high-risk exploration and so forth.
Boy, I really need to go through the archives and mark everything that's been discarded. Which is almost everything.
Fighters vs. eldritch horrors
OTOH, if realspace mass is a treasured commodity, and sea monsters can pop out of nowhere, maybe leaving a chemical trail pointing to you is unhealthy, and chemical-rocket ships vanish without a trace? Short-term rocket weapons and fighter runs are risky but doable (hmm, stellar dogfights with a risk of attracting sharks or worse).
This does necessitate sea monsters either capable of high speed travel or of sensing things coming a long way off. Or that they are very reliably going to catch things before they hit a really high speed.
If they're not reliable in catching every ship/projectile, higher-speed communication might be possible: launch a bunch of signal rockets, one might get through. Though if you're doing a "stargate" thing, it might not be healthy to stick around afterward yourself, since there are two ends to that Exhaust Path That Points To Tasty Mass.
